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Emulsion polymerization of vinyl acetate by urethane based surfactant and high solid content water-based emulsion polymerization of acrylic monomers
Emulsifiers, another name are surfactants, are characterized by a chemical structure comprising a hydrophilic group having one and/or two hydrophobic flexible alkyl chains of a certain length. In small quantities dispersed in the aqueous phase, the surfactant is adequate for self-assembly into the micelle micro aggregates. Surfactants are used in several areas for different purpose such as painting, emulsion polymerizations, adhesives, textile industry, etc. Surfactants are divided into four main categories. They are anionic, cationic, non-ionic and zwitterionic. In this study, a new nonionic polymeric surfactant (PU) has been synthesized with the reaction between Poly(ethylene glycol) dimethyl ether (PEG500) and Toluene 2,4-diisocyanate (TDI). The polymeric surfactant was characterized by using FT-IR spectroscopy, GPC, critical micelle measurements via tensiometer. Critical micelle concentration of PU was determined by surface tension measurements. This value was calculated as 0.68x10 mg / mL. Molecular weight of the PU was determined by gel permeation chromotography (GPC). Mw, Mn and Mz molecular weight was measured as respectively 1361, 1163 and 1524 g / moles. Polydispersity index was obtained as 1.171 . PU was used emulsion polymerization of vinyl acetate and copolymerization of metyl methacrylate and butyl acrylate depending on surfactant quantity and time. Obtained latexes was characterized by particle size measurements, viscosity and surface tension measurements. In addition, molecular weight of the polymers were determined by GPC. High solid content water-based emulsion polymerization studies were performed in the another part of the thesis. Latexes produced by emulsion polymerization are versatile materials. It extensively used in very different industry such as adhesives, coatings, textiles, paper paints, floor polish and makeup. The solids content of the latexes produced in the industry is between 50-55%. High solids content (HSC) brings many advantages, such as maximizing reactor production, minimizing transportation and storage costs, providing greater flexibility in product formulation and improving surface coverage when applied. The increase in solids content negatively affects the latex viscosity. This also affects the heat removal rate, mixing ability, mass transfer and product stability. The way to obtain low viscosity (HSC / LV) high solids content is achieved by controlling the particle size distribution (PSD). Particles in a perfect monodisperse latex will contact the solids content of about 64% theorically. This explains that most industrial processes with relatively narrow particle size distribution generally operate at less than 55% by weight of solids content. Bimodal particle size distribution production is considered to come from above this limitation and to achieve the goals of high solids content and low viscosity. In this thesis, two different methods were used to produce twelve different high solid content emulsion polymerization. Firstly 42 nm seed emulsion was prepared by semi-continuous polymerization. Seed emulsion was grown with pre-emulsion via feeding. After the firstly added seed is required to grow, a precise amount of seed was introduced into the reactor shot wise, keeping the feeding of monomers, surfactant and ammonia to reach the desired solids content. Secondly, primary seed was not used in second method. The rest of experiment conditions are same with first method. 65% solid content latexes are obtained. The latexes were characterized by using, Brookfield viscometer, tansiometer, Zetasizer Nanaoseries NS. Unimodal particle size distributions were obtained at the final product that is produced with first method. Viscosities of these products are quite high, compared with other method. The surface tension of these products raise with increasing solid content. Another products which are produced second method, has bimodal particle size distribution. Viscosities of these products are quite low, due to bimodality. The surface tension of these products has nearly same values because of surfactant amount. To sum up, high solid content low viscosity bimodal and unimodal particle size distribution emulsion polymers were synthesized.
Step-growth polymerization of formaldehyde and paraformaldehyde with amine monomers for preparing monolithic capillary columns
Monolith structures are a big research area of material science with different forms and usages. Monoliths are kind a controlled structure to select some analytes which wants to separate. Monoliths are maden from different materials like silica or polymers. Polymer materials have a wide range applications. Polymers had place of metals and some other materials because of their production methods and chemical properties. Polymeric monoliths are mostly in membrane or column form. Membrane types monoliths produce for enviromental industry or health industry. Seperation could be possible for membrane types monoliths by molecularly imprinting technology. Imprinting technology is like a molding of deserved chemical with a structure of polymer. This provide lots of chemial structure can be separate with monolith structures. Just the important part is matching suitable polymer structure with a suitable mold molecule. Column type monoliths are main research area of seperation technology. After chemical processes developed amount of chemicals inside the mixtures were wanted to analyse with different ways and for analyse seperation is necessary. Chromatographic analysis are main driver of that purpose. Chromatographic analysis are combination of seperation technology with a dedector to calculate amount of analytes. Seperation should be perfect for amount analysis of chemical structures Columns are the most important part of that analysis with different structures. Polymer columns are mostly prepared with in-situ polymerization which means synthesis of polymer inseide of column. And polymer should stay inside of column with high pressures. Monomers and template molecule for imprinting are sending inside of column at same time as a homogenious solution to obtain uniform column. Template molecules can be deserved analyte for analysis or a different analyte with similar structure. For health analysis it is not possible always to find same structure with deserved molecule so similar strucure are used for molecular imprinting. Analysis for cancer diagnostics aim is a new study topic now. For that analysis phospopeptide structures are the most used template molecules. That study is a prestudy of preparing a new type phospopeptide imprinted monolithic cappilary column by polycondensation. For this purpose different amine monomers have used for copolymerization. The amine monomers which have used; biguanide, guanide, biuret and biurea. There was not any new study about this monomers forcopolymerization of formaldehyde so firstly suitable polymerization conditions should be found .Investigation of that condtions is a complicated process.Polymerizayion at high temperature is not possible for molecular imprinting because of structure of template molecules. Bulk format polymerization inside the glass vials have investigated before in-situ polymerization to find best conditions for polymerization. FT-IR analysis have maden to investigaste functional bonds. Spectra showed absorbances of expected bonds. Different temperatures, different amount of monomers and different polymerization times have tried for each monomer. BET surface area analysis have maden for some polymers. Higher amounts formaldehyde and polymerization time above 1 hour caused higher surface area. Before in-situ polymerization, wall of columns have prepared by silanization to making active for keeping polymer inside under high pressures. Mostly APTMS is used for silanization of columns. Different amount of APTMS have tried for that study. Columns have tried with HPLC pump and methanol have used as mobile phase to see silanizasyon results. And the most effective pretreatment ways found. SEM images of that columns have taken to see interaction of column and polymer. That discovered; % 50 amount of APTMS with 80 oC silanization temperature was the best one. And also solvent concentration which are used before APTMS for washing column is also has a little effect for result of silanization. Columns are suitable for high pressure liquid chromatography but molecular imprinting results should investigate more. From all that results it was clear that Phenyl-biguanide and paraformaldehyde polymer monoliths could be useful for preparing phospopeptide imprinted columns by polycondensation. But still there is a lot to do for finding useful columns.
Preparation of urethane modified poly(styrene) based resin for removal of phenol
The human being is influenced by the quality of water resources in the natural environment. In order to guarantee a secure and healthy life, the water consumed must be free from harmful chemical substances. The water released into the environment by water purification plants and private organizations should be regularly accessed and examined to maintain complete yielding to water framework act. Thus, treated waters should be safe for consumption and free from harmful compounds to guarantee a healthy life. However, there are environmental organizations for water quality which have given standards to ensure that water is free from contaminants, thus making safe water consumption possible. Water treatment requires adequate analysis and monitoring which includes determination of low level contaminants. The maximum level of contaminants which present in drinking water should be so small that the effect is harmless to human health. Thus analytical methods are important to quantify the contaminants. Phenol and derivatives are harmful substances found in water. Moreover, faced with more and more stringent regulations, the water contamination has also become noteworthy source of concern and priority for most industrial sectors. Phenols are aromatic components which contain one and more hydroxyl groups connected to aromatic ring. Phenol is a benzene derivative having chemical formula of C6H5OH with a structure of a hydroxyl group bonded to the phenyl ring. It is a colorless, crystalline substance of characteristic odor, soluble in water and organic solvents. Phenols are similar to alcohols but form stronger hydrogen bonds. Thus, they are more soluble in water than alcohols and have higher boiling points. Phenol was prepared mainly from coal tar, in the early 19th century. Presently, small quantities of phenol is still obtained from coal tar. The demand for phenol grew significantly with the commercialization of phenolic resin (Bakelite), during the 20th centuries. An advanced and popular phenol process is Hock Process after the World War II. It is currently the predominate route for the production of phenol which is accompanied by acetone as a co-product. The main commercial plant utilizing toluene as the feedstock was launched in the 1960's. Nowadays, the commercial production of phenol is not obtained from toluene. Phenols are used in many industrial activities for the production of pesticides, insecticides, herbicides, and synthetic products. Phenols in which certain amount of pesticides and wood preservatives contain can lead to specific health damages even at the lowest concentration levels. Some harmful effects of breathing phenol from the air have been occured for human. Short time effects of phenol include breathing infection and eyes burning. The chronic effects of high exposures cause muscle aches, weak spots, weight loss. Effects of long term and low level exposures cause to increases in cancers and effects on the immune system. Nevertheless, it is important to be aware of phenols and substituted phenols in environmental and biological samples. Many different techniques are used for the removal of phenol from wastewater. The methods can be separated into three categories: chemical, biological and physical. All of them have advantages and disadvantages. Because of high cost and disposal problems, many of these conventional techniques for treating phenol bearing wastewater have now not been widely applied at large scale in the textile and paper industries. Adsorption of phenol has three mechanisms; π-π dispersion interaction, electron donor-acceptor complex formation and hydrogen bond formation. In this thesis these mechanism were applied to synthesis new polymeric resins for phenol removal. Two types of polymeric resins were prepared for adsorption of phenol from the water. In the first part of this study, The Resin 1 was obtained with chloro-sulfonated polystyrene (CSPS) and it excess of ethanolamine. The resin was characterized with analytical methods and FT-IR spectroscopy to determine the functional groups. The Resin 2 was prepared through a reaction of the Resin 1 with butyl isocyanate in dimethyl formamide (DMF) solution. Polymers were characterized by using analytical methods and FT-IR. In the second part of the study, experimental measurements were performed on modified resins for phenol adsorption. The phenol sorption capacities of the resins were described by mixing 0.1 g polymer samples (resin1 and 2) with 10 mL phenol solutions with various concentrations (0.5 M, 0.35M, 0.25 M, 0.1M, 0.05 M, 0.025 M and 0.01 M). The phenol loading capacities were calculated from the initial and ending phenol contents of the solutions. Also, kinetics of phenol sorption was performed at low concentration to investigate the efficiency of the modified resin at trace concentration. For this purpose, pseudo-first order, pseudo-second order and intra particular diffusion kinetics models were used.
Research on the mechanical and morphological properties of microfibrillar reinforced PET/PP blends at various processing routes
Polypropylene (PP) is one of the commodity polymers used in a number of industries including packaging, automotive, infrastructure, and textile. However, because of its low mechanical properties, there are some restrictions in its application ranges. Compounding with functional fillers like glass fiber can greatly enhance the mechanical properties of PP. However, this kind of filler is abrasive for production line, not eco-friendly and expensive. Because of that in today's market conditions, producers have been looking for a way to provide more economic and eco-friendly solutions. In recent years, polymer blending has become an economic way for preparing new materials. Some advantages of blending can be listed as below; • Blending can offers customer-driven product design opportunity. • The properties of matrix polymer such as flame resistance, toughness or dimensional stability can be improved. • Blending can offers a way for recycling of industrial plastic wastes. • Blending with low viscosity polymer can improve processability. • Blending can provide to increase of productivity. • Additionally, blending technology can be also used in multi-layer structures. In plastic industry, different ways are used to prepare polymer blends such as melt blending, block or graft copolymerization, melt solution. However, among of these techniques, melt blending is the most commonly used method to achieve desired properties. This method offers opportunity to prepare polymer blends in more economically. As known, most of polymers are thermodynamically incompatible due to differences in their chemical structure. Therefore, during the mixing numerous types of phase morphologies such as fibrillar, droplet or laminar occur and, final properties of blend strongly depend on this morphology. For example, laminar structure of the dispersed phase which is often generated via film extrusion or blow molding improves the barrier properties of blend, whereas fibril structure enhances the mechanical properties. In resent years, a new type of material named as microfibrillar reinforced composites (MFCs) based on blending of two immiscible polymers have been developed. In this materials, to achive higher mechanical performance, minor phase is dispersed in fibrillar form in the matrix polymer. In contrast to the common composites, MFC materials can prepare without any inorganic additives. Additionally, this technology offers opportunity to weight reduction and easy recyclability in comparison to glass fibre reinforced composites. The main aim of thesis study is to produce microfibrillar reinforced PET/PP blends and investigate the effects of various parameters such as screw speed, process temperature, drawing method, drawing ratio, PET content and compatibilizer on the morphological and mechanical properties. In study, microfibril reinforced composites were prepared by a three step process. In the first step, two polymers were blended in a twin screw extruder. In second step, to obtain PET fibers, the extrudate was stretched. In last step, to achive MFC material, drawn PET/PP blends (MFB) were pelletized and molded by injection molding. After each stage of MFC production, analyzes were carried out by scanning electron microscopy (SEM), wide angle X-Ray diffraction (WAXD) and mechanical tests. At the beginning of study, to determine appropriate screw rate for blending, PET and PP were mixed at various screw rates. It was observed from the SEM images that lower or higher screw speeds than 300 rpm were not suitable to obtain homogeneously dispersed blend morphology. In second step of study, to generate microfibril reinforced blend (MFB), two different stretching methods were used. In the first method, the extruded blend was stretched between the first godet and extruder die by increasing rotation speed of first godet. In the second method, the extruded blend was stretched between the two godets. According to the analysis results, reinforcer polymer was able to successfully distributed in fibrillar shape in both methods. However, in second method higher mechanical properties were achieved as a result of well orientation of both component of blend. Depend on the PET concentration and applied draw ratio, the tensile properties of MFB samples greatly increased almost 6-7 times higher than extruded blends. In study, the influence of compatibilizer and its amount on the blend properties were also investigated. SEM images showed that after adding of compatibilizer, maleic anhydride grafted polypropylene (PP-g-MA), more uniform blend morphology was occured. Additionally, adhesion between the PET fibers and PP matrix was improved through compatibilizer and thus, mechanical properties increased. In the last step of study, in order to achive microfibril reinforced PET/PP composites, drawn blend samples were molded at different injection temperatures. SEM images showed that even though injection temperature was set to temperature which is lower than melting temperature of PET, many of fibers lost their shapes and returned into droplet structure. Despite this, better impact resistance and tensile properties were observed in comparison with extruded blend. In conclusion, when take into consideration three stage of microfibrillar reinforced polymer composites (extrusion, drawing and injection molding), the presence of PET fibers caused to increased mechanical properties of extruded blends but the highest increase was obtained in drawn blend samples. Therefore besides of MFC materials, MFBs may also offer an opportunity for industrial applications. For example, it can be weaved like technical textiles or it can be directly winding on products like plastic pipe. On the other hand, MFCs can be used in injection molded plastic pipe parts called as fittings.
Langmuır-Blodgett ince film üretme tekniği ile hazırlanan polimer tabanlı nano ince filmlerin karakterizasyonu ve zararlı organik buharlara karşı duyarlılığı
Bu çalışmada, α-(naftalin-1-yloksi)-2-oksooetil metakrilat polimeri (Poli-NMA) sensör maddesi olarak kullanılarak polimer bazlı kimyasal sensör geliştirilmiştir. Bu amaç için polimer türevi, Langmuir-Blodgett (LB) ince film kimyasal gaz sensör elementi olarak tasarlanmıştır. Poli-NMA maddesi Fourier Dönüşümlü Kızılötesi (FTIR), 1 H-NMR (Nükleer manyetik rezonans) ve 13C-NMR analizleri ile karakterize edilmiştir. Bütün Poli-NMA LB ince filmleri Atomik Kuvvet Mikroskobu (AKM), UV-Görünür Bölge Spektroskopisi ve Kuartz Kristal Mikrobalans (KKM) teknikleri ile karakterize edilmiştir. Polimerik kimyasal sensörü KKM tekniği kullanılarak dört farklı zararlı organik buhara (diklorometan, kloroform, benzen ve toluene) maruz bırakılmıştır. Bu çalışmada, ayrıca, Poli-NMA kimyasal sensörünün zararlı buharlara karşı hassasiyet ve LOD değerleri belirlenmiştir. Oda sıcaklığında elde edilen sonuçlar, polimerik kimyasal sensörün zararlı buharlara karşı tepkisinin geniş, hızlı ve tekrarlanabilir olduğunu ve kinetik tepki değerlerinin sıralamasını diklorometan, kloroform, benzen ve toluen olarak göstermiştir.
Ksantan GAM-G-2-(N-Morfolino) etilmetakrilat/titanyum oksit bazlı yeni yarı iç içe geçen ağ yapılı hidrojellerin sentezi, karakterizasyonu ve katyonik boyaların sulu çözeltiden tek ve rekabetçi adsorpsiyonu
Organik boyaların endüstriyel atık sulardan uzaklaştırılması, çevrenin korunması ve canlı yaşamın devamı açısından özel ilgi çekmektedir. Bu çalışmada, titanyum oksit nanoparçacıkları (TiO2) içeren ksantan gamı (KsG)-graft-poli 2-(N-morfolino) etilmetakrilat (MEMA) bazlı yarı-iç içe geçen hidrojelleri serbest radikalik polimerizasyon yöntemi ile sentezlenmiştir. KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5, metilen mavi (MM+) ve kristal viyole (KV+) boyar maddelerinin tekli ve ikili sulu çözeltilerinden adsorpsiyon metoduyla uzaklaştırılması için etkili bir adsorban olarak kullanılmıştır. Gözenekli yapıya sahip olan hidjellerden KsG-g-poli (MEMA)/TiO2%1,5'nin şişme oranı %481,9 iken KsG-g-poli (MEMA)'nın %447,5'tur. Hidrojellerin sıfır yük noktası 7,8 olarak hesaplanmıştır. Boyar maddelerin sulu çözeltilerden uzaklaştırılması davranışlarında KsG-g-poli(MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5 hidrojelleri için MM+ boyasında Dubinin-Raduskevich (D-R) izotermine ve KV+ boyasında Freundlich izotermine uyum göstermiştir. Kinetik çalışmalar, her iki boyanın KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5 adsorbanı ile adsorpsiyonunun parçacık içi difüzyon modeline uyduğunu ortaya çıkarmıştır. İkili sistem çalışmalarında, KV+'nın uzaklaştırılma yüzdesi MM+'den daha yüksek olarak bulunmuştur. Tekli sistem adsorpsiyon kapasiteleri ile karşılaştırıldığında, ikili sistemde her iki boyanın uzaklaştırılan miktarları daha yüksektir. Buna göre, her iki boyanın da KV+/MM+ karışım çözeltilerinden adsorpsiyonları sırasında sinerjik bir etkileşim gösterdiği sonucuna ulaşılmıştır. MM+ ve KV+ boya karışımlarından adsorpsiyonu için en uygun model yalancı ikinci derece model olduğu belirlenmiştir. Dördüncü adsorpsiyon-desorpsiyon döngüsünden sonra bile, adsorbanın boya çıkarma etkinliğinin nispeten yüksek olduğu belirlendi. KsG-g-poli (MEMA) ve KsG-g-poli (MEMA)/TiO2%1,5, kirli suyun arıtılmasında değerli ve yeniden kullanılabilir bir adsorban olabilmektedir.
Doğal bor mineralleri kullanarak radyasyon dozimetresi geliştirilmesi
Bu tez çalışmasında; iyonlaştırıcı radyasyonun bulunduğu bölgelerde yaşayan ve/veya çalışan farklı sektördeki insanların soğurdukları radyasyon dozunun belirlenebilmesi için, doğal bor minerallerinden radyasyon dozimetresi olarak geliştirilmesi amaçlanmıştır. Bu çalışmada Balıkesir'de Bigadiç bölgelerinden farklı bölgelerinden temin edilen doğal bor minerallerinden Kolemanit-1, Kolemanit-2, İnyoit ve Üleksit kullanılmıştır. Kayaç olarak temin edilen minerallerin yapı analizi X-Işını Difraksiyon Yöntemi (XRD) ve Taramalı Elektron Mikroskop (SEM) ve Enerji Dağılımlı X-Işını Spektroskopisi (EDX) analizi ile gerçekleştirilmiştir. XRD sonuçlarına göre, doğal bor minerali Kolemanit-1 ve Kolemanit-2 monoklinik yapıda olup, kristalit boyutları sırasıyla 39,45 nm ve 39,36 nm'dir. Doğal bor minerali Üleksit triklinik yapıdadır ve kristalit boyutu 41,26 nm'dir. Doğal bor minerali İnyoit ise monoklinik yapıda olup kristalit boyutu 39,37 nm'dir. Yapı morfolojisi için SEM analizi, elementel analiz için de EDX analizi gerçekleştirilmiştir. Elementel analiz sonucunda, doğal bor minerali Kolemanit örneğinin yapısında B,O,Sr,Ca elementleri, doğal bor minerali Üleksit örneğinin yapısında C,O,Na,Ca elementleri, doğal bor minerali İnyoit örneğinin yapısında ise O,Ca elementleri tespit edilmiştir. Tez süresince çalışılan doğal Bor mineralleri farklı ışınlama kaynakları ile cGy (1, 2, 3, 4, 5, 6, 7, 8, 9, 10 cGy), Gy (6,9) ve kGy (1, 2, 3, 4, 5, 6, 7, 8 kGy) mertebelerinde ışınlanmıştır. Bu ışınlama çalışmalarına ek olarak örneklerin UV ışınlama çalışmaları da gerçekleşmiştir. Geliştirilmesi amaçlanan radyasyon dozimetresi malzemesinin incelenmesi, ağırlıklı olarak Elektron Spin Rezonans (ESR) Spektroskopisi ile yapılmıştır. ESR için optimum deney şartlarının belirlenmesi için mikrodalga gücü ve modülasyon genliği çalışmaları yürütülmüş ve optimum mikrodalga gücü 1 mW ve optimum modülasyon genliği 1 G olarak belirlenmiştir. ESR spektroskopisinde önemli bir spektral parametre olan spektroskopik yarılma çarpanı g-değeri; doğal bor minerali Kolemanit-1 ve Kolemanit-2 örneği için sırasıyla 2,0021 ve 2,0011 olarak belirlenmiştir. Doğal bor minerali Üleksit örneği için g-değeri 2,0016 ve İnyoit için ise 2,0009'dur. Tepeden tepeye çizgi genişliği ∆Hpp değeri ise Kolemanit-1 için 4,56 G, Kolemanit-2 için 7,10 G, Üleksit için 6,55 G ve İnyoit için 6,32 G'dir. Tez kapsamında incelenen doğal Bor minerallerinin doza bağımlılıklarının cGy ve Gy ışınlamaları için çok düşük olduğu, kGy mertebesindeki ışınlamalar için ise tüm örnekler için ESR sinyal şiddet değerlerinde artış olduğu görülmüştür. İncelenen numuneler arasında doz- cevap bulguları en yüksek olan numune Kolemanit-1 ve Kolemanit-2 olarak belirlenmiştir. Bununla beraber ışınlanan örneklerinin ESR sonuçları detaylandırıldığında, ışınlanan örneklerin bazı radyasyona hassas ve kararlı rezonans piklerinin dozimetrik amaçlı kullanılabileceği sonucuna varılmıştır. Bu bağlamda ışınlanan doğal Bor minerallerinden oluşturulan doz-cevap eğrileri ve zaman incelemesi çalışmaları irdelendiğinde; Kolemanit-1 ve Kolemanit-2 örnekleri için sırasıyla 2 nolu ve 4 nolu rezonans piklerinin radyasyona duyarlı olmaları ve daha kararlı olmaları (zamana bağlı sönüm oranında azalma Kolemanit-1'de %40, Kolemanit-2'de %20) nedenleri ile doz ölçümlerinde kullanılabileceği sonucuna varılmıştır. Üleksit ve İnyoit için ise, sırasıyla 7 nolu ve 8 nolu rezonans piklerinin toplamının (orta pik) dozimetrik özelliğinin fazla olduğu sonucuna ulaşılmıştır. UV ışınlamanın etkisi ile ışınlanmış ve ışınlanmamış Kolemanit-1 ve Kolemanit-2'de spektrumdaki pik şiddetlerinde anlamlı bir fark olmamıştır, Üleksit ve İnyoit'de spektrumdaki mangan pik şiddetlerinde artış olmuştur. Tez kapsamında; incelenen örneklerin dozimetrik özelliklerinin belirlenmesi amacıyla kullanılan ESR ölçümlerine tamamlayıcı bilgiler verebilmesi amacıyla Termolüminesans (TL) çalışmaları da cGy, Gy ve kGy mertebelerinde ışınlanan örnekler için yürütülmüştür. Gerçekleştirilen TL çalışmaları, ışınlanmış ve ışınlanmamış doğal Bor minerallerinde anlamlı bir farkın olmadığını göstermiştir.
Doğal kauçuk/bütadien kauçuk esaslı elastomerik malzemelerin hazırlanması, karakterizasyonu ve raylı sistem araçlarında birincil süspansiyon titreşim sönümleme elemanı olarak kullanımının incelenmesi
Bu tezin amacı doğal kauçuk ve bütadien kauçuk kullanılarak farklı oranda ve farklı türde karbon siyahları ile hamur sistemlerinin hazırlanması, hazırlanan bu karışımların pişme özelliklerinin incelenmesi ve karakterizasyonun yapılması, karbon siyahının elastomer özelliklerine etkisinin değerlendirilmesi ve hazırlanan karışımların raylı sistem araçlarında birincil süspansiyon olarak kullanılan elastomer esaslı konik yaylarda kullanımının incelenmesidir. Tez kapsamında dört farklı reçete oluşturulmuştur. Reçetelerde doğal kauçuk bütadien kauçuk oranı sabit tutulmuş dolgu maddesi karbon siyahının oranı ve türü değiştirilmiştir. Hazırlanan kauçuk karışımların önce Hareketli Kalıp Reometresinde (MDR) cihazında pişme davranışları incelenmiştir. Pişme özelliklerine göre belirlenen sıcaklık ve sürede hidrolik preste test plakaları üretilmiştir. Hazırlanan test plakaları üzerinden sertlik, kalıcı deformasyon, mekanik testler ve ısıl yaşlandırma testleri yapılmıştır. Kauçuk karışımlarında kullanılan karbon siyahlarının türünün etkisinin değerlendirilmesi ve diğer dinamik mekanik özelliklerinin değerlendirilmesi amacı ile Kauçuk Proses Analizör (RPA) cihazı yardımı ile karışımların farklı frekanslarda depo modül değerleri ve çapraz bağ yoğunlukları bulunmuştur. Karbon siyahının depo modülü üzerindeki etkisini gözlemek amacıyla ayrıca farklı frekanslarda DMA cihazıyla da frekans taraması yapılmıştır. DMA cihazı ile karışımların sönümleme özellikleri de belirlenmiştir. Ayrıca disklerin konik yay ürününde kullanımını değerlendirebilmek için Elastomer Test Sistemi cihazı ile yük altında, farklı frekanslarda tarama yapılarak karışımların sönümleme, doğal frekans, titreşim geçirgenliği ve direngenlikleri değerlendirilmiştir. Elde edilen veriler ışığında karışımlar arasından seçilen NR50 formülü ile elastomer esaslı konik yay hazırlanarak, konik yay için tanımlanan şartname değerlerine uygunluğu ve araçta kullanılabilirliğini incelemek amacı ile elastomer esaslı konik yaya; kalıcı deformasyon, dikey – yanal yük altında yer değiştirme (direngenlik) testleri yapılmıştır. Yapılan çalışmalar ışığında, geliştirilen karışımların elastomer esaslı konik yayda kullanılabileceği kanıtlanmıştır.
Moleküler baskılı floresannanoparçacıkların sentezlenmesi ve sensörsistemlerinde kullanımlarının incelenmesi
Son yıllarda üstün floresans özellikleri, fotokimyasal kararlılıkları ve farklı uygulama alanlarında kullanım kabiliyetleri lantanit (nadir toprak elementi) katkılı üst enerji dönüşümü yapabilen nanoparçacıkların (upconversion nanoparticles - UCNP) farklı birçok alanda ilgi çekmesine ve sıkça kullanılan kuantum dot ve organik boyalara kıyasla tercih edilmesine sebep olmuştur. UCNP yapıları, gün ışığında çıplak gözle görülebilecek şiddetli ışıma yapmaları, toksik olmamaları, yüksek foto kararlılık göstermeleri ve biyouyumlu olmaları gibi nedenlerle tıbbı görüntüleme, tedavi, ilaç salımı, adli bilimler gibi alanlarda sıklıkla kullanılmaktadırlar. Farklı geometri ve boyutlarda sentezlenebilen bu yapıların birçok sensör uygulamasında da başarılı bir şekilde kullanılabildiği görülmektedir. Bu tez çalışmasında, β– fazına sahip iterbiyum (Yb) ve erbiyum (Er) katkılı sodyum itriyum florür (NaYF4) matrisi (β–NaYF4:Yb3+, Er3+) UCNP yapısı olarak sentezlenmiştir. Azoik bir boyar madde olan basic red 9 (BR9) molekülü, model bir bileşik olarak seçilmiş ve bu bileşiğe özgü moleküler baskılı polimer (MBP) ile UCNP yüzeyi modifiye edilmiş ve UCNP temelli floresan bir sensör sistemi geliştirilmiştir. Tez kapsamında UCNP'lerin farklı hidrotermal yöntemler ile sentezleme süreci optimize edilmiş, en uygun sentez yöntemi belirlenmiş ve elde edilen bu nano yapıların karakterizasyonları gerçekleştirilmiştir. Sentezlenen UCNP'lerin yüzeyleri, 3 farklı yöntem ile MBP tabakası ile kaplanmış ve en uygun modifikasyon yöntemi tespit edilmiştir. Belirlenen en uygun yöntem kapsamında, UCNP yüzeyi önce tetraetilortosilikat (TEOS) ile ardından trietoksivinil silan (TEVS) ile modifiye edilmiş ve yüzeylere vinil grupları kazandırılmıştır. Bir sonraki adımda UCNP'lerin BR9 baskılı polimerik yapı ile kaplanması için monomer ve hedef molekül arasında oluşan kompleks kararlılığının spektroskopik yöntemler ile değerlendirilmesi ve tersinir katılmaayrılma zincir transfer (RAFT) polimerizasyonu tekniği ile moleküler baskılı polimer tabakanın UCNP etrafında oluşturulması çalışmaları yürütülmüştür. Elde edilen yapıların morfolojik özellikleri ve kimyasal yapıları fourier dönüşüm spektroskopisi-attenuated total relectance (ATR-FTIR), (aramalı elektron spektoroskopisi (SEM), taramalı elektron spektoroskopisi-enerji dağıtıcı X-ray (SEM-EDX), X ışınları fotoelektron spektroskopisi (XPS), X-ray defraktometresi (XRD) gibi deneysel tekniklerle aydınlatılmıştır. Karakterizasyonları tamamlanan moleküler baskılanmış polimer ile kaplanmış UCNP yapılarının (MBP@UCNP) hedef molekül olan BR9'a karşı bağlanma, tanıyıcılık ve seçicilik performansları değerlendirilmiştir. MBP@UCNP yapılarının yüksek bağlanma kapasitesi ve tekrar kullanılabilirlik gösterdikleri ve diğer boyar maddelere oranla azoik hedef moleküle karşı tanıyıcılık ve seçimlilik sergiledikleri tespit edilmiştir. MBP@UCNP yapılarının en düşük tespit limiti (LOD) değeri 0.7 ppb bulunmuştur ki bu değer literatürle kıyaslandığında oldukça düşüktür. Geliştirilen sensör sisteminin performansı gerçek su numuneleri ile yapılan bağlanma çalışmaları ile de test edilmiştir. Yürütülen çalışmalar neticesinde, model olarak seçilen BR9 varlığında uygulanan yöntemin oldukça başarılı sonuçlar verdiği görülmüştür. Bu durum, farklı hedef moleküllere özgü sensör sistemlerinin benzer deneysel tekniklerle geliştirilebileceğine yönelik önemli bir potansiyel arz etmektedir.
Yarı iletken polimerlerin bant aralıklarının ve osilatör güçlerinin kuantum mekaniksel yöntemlerle araştırılması
Son yıllarda iletkenliklerinin keşfedilmesiyle beraber polimerler birçok uygulamada metallerin yerini almaya başlamıştır. Polimerlerin kolay hazırlanmaları, düşük maliyetleri, korozyona karşı dayanıklı olmaları ve hafif olmaları, onları metaller üzerinde avantajlı kılar. Polimerlerin kendisinin doğrudan herhangi bir metal ile birleştirilmeden de iletken olabileceği ilk kez 1950li yıllarda ortaya çıkmıştır ve o zamandan bugüne yapılan çalışmalar polimerlerin iletkenliğini artırmayı hedeflemektedir. İletken polimerlerin kullanım alanlarına örnek olarak organik güneş pilleri, elektronik devreler, organik ışık yayan diyotları, aktüatörler, kimyasal ve biyo-sensörler gösterilebilir. Polimerlerde iletkenlik bant aralığı teorisi yardımıyla ii açıklanır. Eğer enerji düzeyinde valans bandı ile iletkenlik bandı arasında 9 eV veya daha fazla potansiyel farkı varsa bu polimer yalıtkandır. Bu potansiyel farkı 0,1 ile 4 eV arasında değişiyorsa bu polimerin yarı iletken olduğunun işaretidir. İletken polimerlerde ise valans bandı ile iletkenlik bandı iç içe geçmiş durumdadır. Polimerlerin iletkenlik özellikleri hem deneysel hem de teorik yollarla çalışılabilmektedir. Deneysel tekniklerde güvenilir sonuçlar elde edilmesine karşın, laboratuvar ortamında yapılan sentezleme ve ayrıştırma işlemleri sebebiyle zamana ihtiyaç duyulmaktadır, fakat teorik çalışmalarla bu işlemlere gerek kalmadan yalnızca bilgisayarlar ve gelişmiş yazılımlar sayesinde polimerlerle ilgili birçok bilgi kolaylıkla elde edilebilmektedir. Teorik çalışmaların önemli bir kolu olan kuantum mekaniksel yöntemler Yarı deneysel (Semi-Empirical), Ab Initio ve Yoğunluk Fonksiyoneli Teorisi (DFT) olarak sıralanabilir. Bu çalışmada poliasetilen (trans ve cis yapılı), politiyofen, poli(p-fenilen) ve poli(p-fenilen vinilen)'in Ab Initio tekniklerinden olan tekli uyarılmış konfigürasyon etkileşimi yöntemi (CIS) yoğunluk fit edilmesi tekniği (DF) kullanılarak bant aralıkları ve osilatör güçleri değerleri hesaplanmıştır. Aynı polimerlerin bu değerleri bir de TD-DFT (zamana bağlı yoğunluk fonksiyonel teorisi) tekniğiyle elde edildikten sonra her iki yöntem hem birbiriyle hem de literatürdeki deneysel verilerle kıyaslanmıştır. Elde edilen sonuçlar göstermektedir ki, TD-DFT tekniğiyle elde edilen bant aralığı değerleri deneysel verilere çok yakınken, CIS metodu ile hesaplanan değerler hem TD-DFT değerlerinden hem de deneysel sonuçlardan belirli bir miktar yüksektir.
Demattia-esnek çatlama test cihazının tasarımı ve elastomerler testlerinde kullanılması
Bu tez kapsamında geliştirilen Demattia-Esnek Çatlama test cihazı elastomerlerin dinamik koşullarda çatlamaya karşı dayanımlarının test edilmesi amacıyla kullanılan ve ülkemizde henüz üretilmeyen ve tamamen ithal edilen bir cihazdır. Cihazın uluslararası standartlara uygun olması için ve standartlara uygun tasarım yapılabilmesi için çalışmanın ilk bölümünde gerekli standartlar incelenmiştir. Ayrıca, farklı marka muadil ürünler de incelenmiş, kullanıcı yorumları alınmıştır. Bu sayede tasarım aşaması için gerekli bilgiler derlenmiştir. Bunun yanında dinamik yorulmaya sebep olan nedenler literatürden taranarak teze eklenmiştir. Çalışmanın ikinci bölümünde test cihazı için kavramsal tasarımlar hazırlanmış, bunların içerisinde detay tasarıma geçilecek kısımlar belirlenmiş ve detay tasarım aşamasında mekanik ve elektronik tasarım sonuçlandırılmıştır. Bu sonuçlara göre hazır ürünlerin seçimleri yapılmıştır. Bu çıktılarla beraber mekanik üretim dokümanları ve ürün listesi hazırlanmıştır. Hazırlanan cihaz için Aktaş Grup Hava Süspansiyon Sistemleri, Ltd. Şti. ve Babacan Endüstri ve Kauçuk Ürünleri İmalatı San. Tic. Ltd. Şti'nden temin edilen numuneler geliştirilen test cihazı ile test edilmiştir. Belirlenen esnek çatlama test süreleri bu test numunelerini üreten firmaların test laboratuvarlarında elde edilen sonuçlarla karşılaştırılmıştır. Tüm örnekler için aynı sonuçlar elde edilmiştir. Ömür testleri başarıyla tamamlanmış, güvenilir, kullanıcı ihtiyaçlarına uygun ilk yerli ve milli bir esnek çatlama test sistemi geliştirilmiştir.
Geri sekme esnekliği ölçüm cihazı tasarımı ve elastomer testlerinde kullanılması
Geri sekme esnekliği ölçüm cihazı elastomerlerin esnekliğinin belirlenmesi amacıyla kullanılan ve ülkemizde üretilmeyen, ithal edilen bir cihazdır. Tasarıma başlanmadan önce referans alınacak standartlar belirlenerek incelenmiş ve cihazın sahip olması gereken özellikler listelenmiştir. Bu bilgiler kullanılarak cihazın detaylı tasarımı yapılmış, kullanılacak hazır ürünler belirlenmiştir. Tasarlanan geri sekme ölçüm cihazının parçalarının uygun teknikler ile üretilmesinin ardından cihaz montajlanarak çalışır hale getirilmiştir. Daha sonra cihazın çalışmasının doğrulanması için standart test yöntemlerinde belirtilen sürtünme ve sarkaç periyoduna bağlı indirgenmiş sarkaç boyu hesaplanmıştır. Bunun yanı sıra Ferkan A.Ş. ve Standart Profil A.Ş. firmalarında farklı cihazlar ile ölçülerek geri sekme esneklik değeri belirlenen numuneler ile karşılaştırmalı ölçümler yapılmıştır. Elde edilen sonuçlar gereksinimi karşılamadığı için tasarım değişlikleri yapılmıştır ve cihaz gereksinimleri sağlayacak şekilde revize edilmiştir. Yapılan güncelleme sonrasında doğrulama testleri ve karşılaştırmalı ölçümler tekrarlanarak cihazın doğruluğu kontrol edilmiştir. Doğrulama için kullanılan numunelerden farklı olarak doğal kauçuk temelli 4 tane farklı reçetede hamur hazırlanmıştır. NR 50 ve NR 60 kodlu reçeteler arasında FEF 550 karbon siyahı oranı arttırılmıştır. NR-MT 50 ve NR-MT 60 kodlu reçetelerde ise FEF 550 oranı sırası ile NR50 ve NR60 reçeteleri ile aynı tutulmuş ve ek olarak aynı oranda MT 990 eklenmiştir. Hazırlanan numunelerin üretilen cihazda geri sekme esneklik değerleri ölçülmüştür. Yapılan ölçüm sonucunda, NR 50 reçeteli numunenin %71, NR-MT 50 reçeteli numunenin %74, NR 60 reçeteli numunenin %52, ve NR-MT 60 reçeteli numunenin %70 geri sekme esnekliği olduğu görülmüştür. 50 shore A sertlikteki NR içine MT 990'ın eklenmesi sertliğini değiştirmediği gibi geri sekme değerini de değiştirmemiştir. 60 sertlikte FEF 550 ve HAF 330 kullanılarak hazırlanan NR için elde edilen %53 geri sekme esnekliği değerinin MT 990 eklenmesiyle hızla %70 düzeyine çıktığı görülmüştür. Bu durumda geri sekme davranışının elastomerin hazırlanmasında kullanılan karbon siyahının tipine ve elastomerin shore A sertliğine bağlı olarak değişim gösterebileceği ancak sistematik ilişkinin kurulabilmesi için daha farklı karbon siyahı oranları ve sertlik değerleri ile çalışılması gerektiği sonucuna varılmıştır.
Arsenik iyonlarının adsorpsiyonunda kullanılan poli(1-vinilimidazol) aşılanmış polimerik adsorbent hazırlanması
Bu tez çalışmasında, tersiyer amin fonksiyonel gruplara sahip yeni polistiren esaslı anyon değiştirici (PS-VIM) adsorbent malzeme, 1-vinilimidazolün klorometil polistiren polimerik partiküller üzerine ATRP aşı polimerizasyonu reaksiyonu ile sentezlenmiştir. 1-vinilimidazol monomerinin klorometil polistiren polimerik partiküller üzerine aşılanma derecesi %83,65 olarak bulunmuştur. Polimerik adsorbent malzemenin yapısal ve morfolojik özellikleri FTIR, SEM ve EDX kullanılarak analiz edilmiştir. 1-vinilimidazol aşılanmış polistiren esaslı polimerik partiküllerin As(V) adsorpsiyon özellikleri incelenmiştir. Çözelti pH'ı, temas süresi, As(V) başlangıç derişimi, iyonik şiddet ve girişim yapan anyonların adsorpsiyon üzerindeki etkileri kesikli adsorpsiyon deneyleri ile 25 °C'da incelenmiştir. As(V) iyonlarının adsorpsiyonunun pH'a bağlı olduğu ve maksimum adsorpsiyonun pH 5,00'te gerçekleştiği tespit edilmiştir. Kinetik çalışmalar, As(V) iyonlarının PS-VIM polimerik partiküller üzerine gerçekleşen adsorpsiyon işleminin, yalancı ikinci dereceden reaksiyon modeline (R2=0,9902) uyduğunu göstermiştir. As(V) iyonları için PS-VIM adsorbentinin adsorpsiyon izoterminin Langmuir modeline uyduğu bulunmuştur. As(V) iyonlarının maksimum adsorpsiyon kapasitesi, Langmuir izoterminde pH 5,00'te 90,10 mg/g adsorbent olarak belirlenmiştir. Çözeltinin iyonik şiddetinin NaCl ile artması, As(V) iyonlarının adsorpsiyonunu etkilediğini göstermiştir. Adsorbent ve adsorbat arasındaki etkileşimin, elektrostatik etkileşim olduğu tespit edilmiştir. As(V) iyonlarının adsorpsiyonu, Cl-, NO3-, SO42- ve PO43- gibi girişim yapan iyonların varlığında incelenmiş ve SO42- iyonlarının As(V) iyonlarının adsorpsiyonunu önemli ölçüde etkilediği, ancak Cl- iyonlarının en az etkiye sahip olduğu bulunmuştur. On adsorpsiyon-desorpsiyon döngüsü, polimerik malzemenin, As(V) iyonlarının sulu çözeltiden verimli bir şekilde uzaklaştırılması için uygun olduğunu göstermiştir. Adsorbent olarak kullanılan PS-VIM polimerik partiküllerinin yüksek derişimlerde As(V) iyonları içeren çeşme sularından arsenik iyonlarını uzaklaştırdığı gösterilmiştir. Bu tez çalışmasında elde edilen sonuçlardan, PS-VIM polimerik partiküllerin As(V) iyonlarının sulu çözeltilerden uzaklaştırılması için etkili bir adsorbent malzeme olarak kullanılabileceği sonucuna varılmıştır.
Silikon elastomerlerin sönümleme özelliğini kontrol eden yapısal parametrelerin belirlenmesi
Silikon kauçuklar günümüzde endüstride geniş bir kullanım alanına sahiptir. Diğer kauçuk türlerine göre birçok avantajı vardır. Bunlardan başlıcaları; yüksek ve düşük sıcaklıklarda özelliklerinin değişmemesi, iklim koşullarından etkilenmemesi, çok yüksek yalıtım özelliği göstermesidir. Bu ve bunun gibi birçok avantajından dolayı günümüzde elektrik-elektronik sektörü, otomotiv sektörü, gıda, tıp ve inşaat sektöründe sıklıkla kullanılmaktadır. Ses, basınç dalgalanmaları tarafından yaratılan bir olgudur. Ancak sürekli ses makinelerde enerjinin boşa harcanmasına neden olmaktadır. Silikon elastomerler de yüksek sönümleme kapasitesine sahip olmasından dolayı makinelerde boşa harcanan enerjinin engellemesinde oldukça önemli bir yere sahiptir. Bu tezde silikon elastomerlerin enerji sönümleme özelliklerini kontrol eden yapısal parametrelerin belirlenilmesine çalışılmıştır. İlk olarak farklı kaynaklardan elde edilen silikon tipleri kullanılarak karışımlar hazırlanmıştır. Hareketli Kalıp Reometresinde (MDR) 180 oC ve 20 dakika süresince karışımların pişme özellikleri incelenmiştir. MDR cihazındaki sonuçlardan en yüksek delta tork değeri Silplus 80 silikonunda elde edilmiştir. R752/50 ise en düşük delta tork değerine sahiptir. Kopma uzama eğrileri incelendiğinde en fazla uzamanın R752/50 silikon elastomer örneğine ait olduğu görülmüştür. Silplus 80 ve Ravasil 70 örneklerinde en az uzama değeri elde edilmiştir. Çapraz bağ yoğunluğu Kauçuk Proses Analizörü (RPA) cihazında frekans taraması yapılarak belirlenmiştir. En yüksek çapraz bağ yoğunluğuna sahip olan örnek Silplus 80 silikon elastomerinde elde edilmiştir en düşük çapraz bağ yoğunluğuna sahip olan elastomer R752/50'dir. Pişmiş ve pişmemiş örneklerde gerinim taraması yapmak için frekans 1,0 Hz'de sabit tutulurken, 50 oC'da gerinim taraması yapılmıştır. Gerinim aralıkları ise 0,007-12,942 o'dir. Strain (gerinim) taraması malzemedeki Payne etkisini görmek amacıyla yapılmıştır. En büyük delta G' değerleri arasındaki fark Silplus 70 örneğinde görülmüştür. En düşük G' değerleri arasındaki fark R752/50 örneğine aittir. G' değerinin küçük olması da daha düşük Payne etkisi, daha güçlü dolgu maddesi-polimer etkileşimi ve daha iyi dolgu maddesi dağılımı anlamına gelmektedir. Termal Gravimetrik Analiz (TGA) sonuçlarına baktığımızda en yüksek bozulma sıcaklığı Ravasil 70 örneğine ait olup sıcaklık değeri de 606,0 oC'dir. En düşük bozulma sıcaklığı R752/50 örneğimize ait olup 532,5 oC'dir. Silikon elastomerlerin bu temel karakterizasyon çalışmalarından sonra enerji sönümleme özellikleri incelenmiştir. Bu amaçla, Sıcak pres kullanılarak disk şeklinde örnekler hazırlanmıştır. Hazırlanan disklere Evrensel Test Cihazı kullanılarak tek yönlü %10,%20,%30, %40 ve %50 oranlarda 10 döngülü sıkıştırma testi yapılmıştır. Sıkıştırma testi verilerinden yararlanılarak birim hacim başına absorplanan enerji değerleri bulunmuştur. Hareketli kalıp reometresinde de en yüksek delta tork değerine sahip olan Silplus 80'in en yüksek absorplanan enerji değerine sahip olduğu görülmüştür. Bu çalışmaların sonunda enerji sönümleme özellikleri ile silikonun sertlik ve çapraz bağ yoğunluğu gibi yapısal parametreleri ile enerji sönümleme özellikleri arasında bir ilişkinin olduğu görülmüştür. Çapraz bağ yoğunluğu artırılarak enerji sönümleme özelliğinin artırılacağına varılmıştır. Anahtar Kelimeler: Silikon elastomer, sönümleme, payne etkisi, çapraz bağ yoğunluğu, reoloji
Hacimsel iskelet kası hasarları için polimer bazlı destek malzemelerin geliştirilmesi
Önemli bir sosyal ve ekonomik yükü oluşturan hacimsel kas kayıpları her yıl milyonlarca insanı kazalar, savaşlar ve tümör operasyonları sebepleri ile etkilemektedir. İskelet kası yapısı doğal onarım mekanizmasına sahip olmasına rağmen, kritik seviyenin üzerindeki kayıplarda kendi kendine iyileşmeyi sağlayamamaktadır. Bu durum ciddi oranda fonksiyonel hasarlar ve estetik eksikliklerle sebep olmaktadır. İskelet kası doku mühendisliği yaklaşımlarında hacimsel kas kaybını desteklemek ve hücresel davranışları yönlendirmek için fonksiyonel doku iskelesi tasarımlarına odaklanılmıştır. Bu tez çalışmasında, hacimsel iskelet kası hasarları için polimer bazlı destek malzemelerin geliştirilmesi amaçlanmıştır. Bu amaç için doğal kas dokusunu taklit edebilmek amacıyla hizalanmış, hücresel gelişimi ve yönelimi destekleyecek seviyede elektriksel aktiviteye sahip poli(ε-kaprolakton) (PCL) bazlı fiber iskeleler hazırlanmıştır. Fiber iskelelerin üretimi için bilgisayar destekli Döngüsel Islak Eğirme Düzeneği (DIED) geliştirilmiştir. İletken özelliğe sahip gümüş nanoteller (AgNT) ile katkılanmış PCL-AgNT kompozit fiberler yüksek verim ile üretilmiştir. DIED üretim parametrelerinin; PCL molekül ağırlığı, çözücü sistemi, çöktürme banyosu sıcaklığı, PCL ve AgNT derişimleri vb. optimizasyonu gerçekleştirilmiştir. Fiberlerin kimyasal, morfolojik, ısıl özellikleri ve biyobozunma davranışları karakterize edilmiştir. C2C12 fare myoblast iskelet kası hücrelerinin elektriksel uyarım altında ve elektriksel uyarım uygulanmadan PCL ve PCL-AgNT kompozit fiber iskeleler üzerindeki çoğalma davranışları ve morfolojileri incelenmiştir. Hücre kültür çalışmalarının 7. gününde, 1.5 V ile 3 V elektriksel uyarım gerilimi altında PCL-AgNT kompozit fiber iskele yüzeylerinde PCL fiberler göre daha fazla hücre çoğalması ve canlılığı gözlenmiştir. Tez çalışması kapsamında DIED ile antibakteriyel özelliğe sahip kompozit fiber formülasyonları geliştirilmiştir. Antibakteriyel ilaç etken madde sülfatiyazol - AgNT kompleksi hazırlanmış ve kompozit fiber üretimi DIED ile gerçekleştirilmiştir. Sülfatiyazol - AgNT yüklü fiberlerin antibakteriyel özellikleri disk difüzyon testi ile 4 farklı bakteri türü için incelenmiş, yüksek başarı elde edilen bakteri türleri ile erken aşama bakteriyel tutunma çalışmaları gerçekleştirilmiştir. Sonuç olarak, PCL-AgNT kompozit fiberler ve antibakteriyel formları iskelet kası doku destek malzemeleri adayı olarak başarılı ve umut vaat edici özellikler sunmuştur.
Stronsiyum-nano zeolit A ile desenlenmiş üç boyut baskılı poli(laktik asit) kemik doku iskelelerinin geliştirilmesi
Kemik hasarlarında polimer bazlı destek malzemelerin kullanımı artan bir hızda devam etmektedir. Polimerlerin biyouyumlu, biyobozunur özelliklerinin olmasının yanı sıra 3B yazıcılarda kullanılabilmeleri sayesinde kişiye özel bir üretim yapılabilmesi bu artışın sebepleri arasında verilebilir. Bu tez çalışmasında üç boyutlu (3B) yazıcıda fused deposition modeling (FDM) teknolojisi kullanılarak poli(laktik asit) (PLA) bazlı destek malzemelerin üretilmesi ve yüzey modifikasyonu ile kemik hasarlarında kullanılmak üzere geliştirilmeleri amaçlanmıştır. 3B yazıcıda basılıcak olan malzeme SolidWorks programında çizilmiş, daha sonra 3B yazıcıda 180 oC'de nozzle ucunun sıcaklığında basım gerçekleştirilmiştir. 3B yazıcıda basım için PLA'nın seçilmesinin sebebi biyouyumlu ve FDA onaylı bir polimer olmasıdır. Ayrıca PLA kemik rejenerasyonu için uygun mekanik özelliklere ve biyobozunma süresine sahiptir. 3B basım öncesi ve sonrası PLA'nın kimyasal ve ısıl özellikleri sırasıyla FTIR ve DSC ile karakterize edilmiştir. İkinci aşama olarak üretilen PLA kemik destek malzemelerin yüzey modifikasyonunda kullanılacak olan nano ve mikro zeolit A tozlarının sentezleri gerçekleştirilmiştir. Sentezlenen nano zeolit A tozlarının boyutları 150-250 nm arasında değişiklik gösterirken, mikro zeolit A tozları 1-1.5 μm boyutlarındadır. Nano ve mikro zeolit A tozlarının karakteristik pikleri XRD ile konfirme edilmiştir. Kemik yapısında bulunan en önemli elementlerden biri olan stronsiyum (Sr) iyon değişimi yöntemi ile zeolit A yapılarına yüklenmiştir. Sr yüklenen Zeolit A yapıları EDX ve XRD ile karakterize edilmiştir. 3B basılmış PLA malzemelerinin zeolitler ile yüzey modifikasyonu için üç farklı yöntem uygulanmıştır. Bu yöntemler sonunda ortaya çıkan ürünlerin kimyasal, ısıl ve morfolojik özellikleri incelenmiştir. Katman biriktirme tekniği ile yüzeyi nano ve mikro zeolit A, Sr yüklü nano ve mikro zeolit A ile dekore edilen PLA kemik destek malzemelerinin biyobozunma ve hücre kültür performansları değerlendirilmiştir. Zeolitler ile yüzey dekorasyonu PLA yüzeylerinde hidrofilik karakterin ve serbest yüzey enerjisinin artmasına sebep olmuştur. Saos hücreleri 14. gün sonunda zeolit modifiye edilmiş PLA yüzeylerinde, kontrol PLA'a göre daha fazla Alkalen Fosfataz (ALP) aktivitesi göstermişlerdir. Tez çalışmasında Sr yüklü zeolit A ile yüzeyi modifiye edilmiş PLA yapılarının kemik doku iskelesi olarak kullanılması yönünden olumlu ve umut verici bulgular elde edilmiştir.
Silikon elastomerlerin ömür süresine etki eden parametrelerin belirlenmesi
Silikon kauçuklar sentetik kauçuk grubuna aittir. Hava şartlarına karşı yüksek direnç, iyi elektriksel özellikler, geniş sıcaklık aralığında çalışma ve kolay işlenebilirliği gibi birçok kullanım avantajı mevcuttur [1]. Bu özelliklerinden dolayı, dış mekan yalıtım uygulamaları ve elektrik iletim ve dağıtım sistemleri gibi uygulamalarda sıklıkla kullanılmaktadır Mükemmel özellik ve dayanıklıklarına rağmen silikon kauçuklar çeşitli çevresel ve kimyasal etkenlere ve yüksek sıcaklara maruz kaldığında zamanla bozunmaya maruz kalırlar Bu bozunma ''yaşlanma '' olarak adlandırılmaktadır. Yaşlanma bir malzemenin istenilen özelliklerinin bozunması sonucunda oluşmaktadır Yaşlanmanın malzeme özellikleri üzerindeki etkilerini anlamak için ömür tahmini yapılmaktadır. Ömür tahmini malzemeyi iyileştirme açısından önem kazanmaktadır
Sıcaklık taramalı gerilim gevşemesi (TSSR) yöntemi ile vinil metil silikon (VMQ) elastomerinin çapraz bağ yoğunluğunun belirlenmesini sınırlayan koşullar
Bu çalışmanın temel amacı, farklı sertliklerde vinil metil silikon (VMQ) elastomerlerin durulma davranışlarının sıcaklık taramalı gerilme durulma (TSSR) cihazında belirlenmesi ve bu cihaz ile çapraz bağ yoğunluğunun bulunmasını sınırlayan koşulların incelenmesidir. Daha önce TSSR cihazı ile 50, 60, 70 Shore A gibi farklı sertliklerde vinil metil silikon elastomerleri ile yapılan çalışmalarda çapraz bağ yoğunluklarının hesaplanamadığı görülmüştür. Bu zamana kadar bu polimerler ile ÇBY değerinin neden gözlenemediği, bunu sınırlandıran koşulların neden olduğu yaklaşımından yola çıkılarak bu çalışma yapılmıştır. Sertliğin, buna bağlı olarak moleküler kütlenin silikon elastomerlerin durulma özelliklerinin üzerindeki etkisini incelemek amacıyla 10 Shore A sertlikten 60 Shore A sertliğe kadar VMQ ile karışımlar hazırlanmıştır. VMQ karışımlarının kürleşme özelliklerinin ve çapraz bağ etkinliğinin karşılaştırılması amacıyla TAIC (trialil izosiyarünat) ve ZDA (çinko akrilat) gibi farklı hızlandırıcı ko-ajanlar kullanılarak karışımlar oluşturulmuş farklı metotlar ile çapraz bağ yoğunlukları hesaplanmıştır. Farklı sertliklerde ve farklı yardımcı ko-ajanlar kullanılarak hazırlanan karışımların kür karakteristiklerinin incelenmesi ve optimum kürleşme koşullarının belirlenmesi amacıyla Hareketli Kalıp Reometresi (MDR) kullanılmıştır. Farklı sertliklerde minimum tork (ML) ve maksimum tork (MH) değerleri incelenip kürleşme dereceleri belirlenmiştir. Aynı sertlikteki silikonlar için TAIC ve ZDA içeren karışımların karşılaştırması yapılmış, ko-ajanların kürleşme özelliklerine etkisi incelenmiştir. Reolojik özellikleri göz önünde bulundurularak test numuneleri oluşturulup TSSR cihazında gevşeme (durulma) özellikleri test edilmiştir. Testin ilk aşaması olan izotermal gevşeme aşaması için karışımların 23 °C'de 2 saat boyunca gevşeme davranışları incelenmiştir. Testin ikinci aşaması olan izotermal olmayan gevşeme aşamasında ise karışımların sıcaklık ile gevşeme davranışları incelenmiş, cihazdan elde edilen çapraz bağ yoğunluğu (ÇBY) değerleri değerlendirilmiştir. Cihazdan elde edilen çapraz bağ yoğunluğu değerlerine ek olarak, izotermal olmayan durulma eğrilerinin eğimleri harici bir yazılım ile bulunmuş ve lastiki-elastiklik eşitlikleri yardımıyla ÇBY değerleri hesaplanmıştır ve cihazdan elde edilen değerler ile karşılaştırması yapılmıştır. Elde edilen ÇBY değerlerinin doğrulamasını yapmak amacıyla kauçuk proses analizörü (RPA) ile frekans taraması çalışmaları yapılmış ve çapraz bağ yoğunluğu değerleri hesaplanmıştır. Yapılan çalışmalar sonucunda elde edilen veriler ışığında TSSR cihazından ÇBY elde edilemediği durumlar incelenmiştir ve olası sebepleri irdelenmiştir. Tüm bu çalışmaların sonucunda artan ÇBY ile gerdirilmiş VMQ elastomerlerin yüksek oranda gerilmeye tepki olarak daha yüksek gevşeme, izotermal durulma ve gerilme miktarlarına sahip olduğu görülmüştür. İzotermal olmayan testlerde ise sertlik arttıkça gerilim bölgesindeki ilk artış eğiminde bir azalma yaşandığı görülmüştür. İçerdikleri fonksiyonel vinil grubu sayısına bağlı olarak, ZDA içeren elastomerlerin ÇBY değerleri TAIC içerenler ile kıyaslandığında TAIC içeren sistemlerin daha yüksek ÇBY değerine sahip olduğu görülmüştür. Çalışmalar aynı zamanda ÇBY değerinin silikonların TSSR uygulamaları için kritik bir parametre olduğunu göstermiştir. RPA yöntemi ile yapılan çalışmalar sonucunda elde edilen çapraz bağ yoğunluğu değerlerinin TSSR yöntemi ile elde edilen değerlere oldukça yakın olduğu belirlenmiştir. Bu da TSSR yönteminin VMQ elastomerler için ÇBY değerinin belirli bir değerin altında kalmak koşuluyla kullanılabileceğini göstermiştir. Anahtar Kelimeler: Çapraz bağ yoğunluğu, Elastomer, TSSR, VMQ
Yüksek sönümleme özelliğine sahip epiklorohidrin esaslı elastomerlerin hazırlanması ve karakterizasyonu
Yüksek sönümleme kapasitesine sahip, farklı polimerik malzemeler titreşimi azaltmak amacıyla endüstride farklı uygulamalarda kullanılmaktadır. Bu malzemelerin çoğunun, sönümleme kapasitesi açısından birçok alanda yetersiz kalmasının yanında yağ, ısı ve kimyasal dayanımlarının düşük olduğu bilinmektedir. Epiklorohidrin (ECH) esaslı ticari olarak Hidrin adı ile bilinen polimerlerin yapısının içerisinde bulunan doymuş uç gruplar ısı, kimyasal ve ozon dayanımının geliştirilmesini ve etilen oksit yapısındaki oksijen polaritesi sayesinde de çok iyi yağ ve yakıt dayanımını sağlar. Bununla birlikte yüksek sönümleme özellikleri sunmaktadır. Bu tez kapsamında yüksek sönümleme özelliğine sahip poli(epiklorohidrin) (ECH yada CO) homopolimeri ve poli(epiklorohidrin-ko-etilen oksit-ko-allil glisidil eter) (GECO) terpolimeri karışımları hazırlanmıştır. Pişirici kimyasal türü, reçine tipi, dolgu miktarı ve homopolimer ve terpolimerlerinin harmanlarının sönümleme davranışı ve fiziksel özelliklere olan etkisi incelenmiştir. Pişirici sistemlerin sönümleme davranışına olan etkisinin araştırılması amacıyla, etilen tiyoüre (ETU) ve Zisnet F-PT marka tritiyosiyanürik asit (TTCA) pişirici kimyasallar olarak kullanılmıştır. Reçine tipinin etkisinin araştırılması amacıyla, C8/C9 aromatik hidrokarbon reçine, C9/C10 aromatik hidrokarbon reçine, fenolik reçine ve sıvı bütadien polimer kullanılmıştır. Dolgu miktarındaki etkiyi incelemek için silan bağlayıcı ajan ile modifiye edilmiş silika 20 phr ve 40 phr oranlarında kullanılmıştır. Harman etkisinin incelenmesi amacıyla epiklorohidrin homopolimer ile epiklorohidrin terpolimerin eşit oranda karıştırılmasıyla sönümleme davranışı araştırılmıştır. Sönümleme davranışlarının incelenmesi amacıyla; sıcaklığa bağlı kayıp faktörü (tanδ) değeri dinamik mekanik analiz cihazı (DMA) ile ölçülmüş olup, geri sekme test cihazı kullanılarak geri sekme testi ve evrensel mekanik test cihazı kullanılarak basma deneyi yapılmış ve enerji sönümleme miktarları değerlendirilmiştir. Hazırlanan elastomerlerin özelliklerinin değerlendirilmesi amacıyla; MDR cihazı ile pişme ve reolojik özellikler, mekanik test cihazı ile çekme testi yapılarak mekanik özellikler, kauçuk proses analizörü (RPA) ile çapraz bağ yoğunluğu ve işlenebilirlik özellikleri ve sertlik test cihazı ile sertlikleri değerlendirilmiştir. TTCA kullanımı ile sönümleme davranışı değişmeden, mekanik özelliklerde büyük ölçüde artış görülmüştür. Fenolik reçine kullanımının, poliepiklorohidrin homopolimeri ve terpolimeri için aktif sönümleme sıcaklık aralığını (tanδ>0,3) arttırdığı görülmüştür. Dolgu miktarındaki artış ile aktif sönümleme aralığı büyük ölçüde değişmemiş olup, mekanik özellikler iyileşerek, işlenebilirliğin zorlaştığı görülmüştür. Poliepiklorohidrin homopolimeri ve terpolimerinin harmanlanması ile sönümleme sıcaklık aralıklarının istenilen sıcaklığa uygun sönümleme seviyesi elde edilecek şekilde ayarlanabileceği kanıtlanmıştır. Yapılan bu çalışma sonucunda, pişirici kimyasal türünün, reçine tipinin, dolgu miktarının ve epiklorohidrin polimer harmanlarının kullanımı ile sönümleme davranışının ECH polimerleri için nasıl kontrol edildiği aydınlatılmıştır.
Peptit ve protein-PEG konjugatlarının sentezi ve kütle spektrometrik analizi
Tedavi edici proteinler farmakoloji alanında oldukça fazla kullanılmalarının yanı sıra, bu alanda tedavi edici protein yapılarını içeren hibrit moleküllerin kullanıldığı birçok klinik uygulama da bulunmaktadır. Polietilen glikol (PEG) kullanılarak, sadece tedavi edici proteinler ile değil tedavi edici diğer bir takım biyomoleküller ve ilaçlarla da pegilasyon adı verilen konjugasyon işlemi gerçekleştirilip hibrit moleküller oluşturulmaktadır. Bu çalışmalarda karşılaşılan en büyük zorluklardan biri, pegilasyon işlemi sonucunda elde edilen moleküllerin analiz edilmeleri, bağlanma bölgelerinin ve bağlanma oranlarının doğru şekilde belirlenebilmesidir. Oluşturulan polimer esaslı bu tedavi edici hibrit moleküllerin analizleri ve karakterizasyonları analitik açıdan oldukça zorlu olmaktadır. Bu tez kapsamında hibrit peptit-polimer ve protein-polimer molekülleri sentezlenerek, bu hibrit moleküllerin analizi ve karakterizasyonları için daha kolay ve zaman almayan analitik yöntemlerin geliştirilmesi amaçlanmıştır. Bu amaç doğrultusunda PEG ile konjugasyona girmesi hedeflenen örnek polipeptit yapıları olarak insan anjiyotensin II ve insan insülini molekülleri kullanılmıştır. Konjugasyon reaksiyonu için farklı molekül ağırlığı dağılımına sahip PEG örnekleri kullanılmıştır. Kullanılan bazı PEG zincirlerinin uç grupları türevlendirilerek farklı reaktif gruplar haline getirilmiştir. Konjugasyon reaksiyonları hem organik çözücü içerikli hem de fizyolojik ortam koşullarında gerçekleştirilmiştir. Son ürün olarak elde edilen hibrit moleküllerin yani konjugatların MALDI-MS sistemi kullanılarak kütle spektrometrik analizleri yapılmıştır. PEG zincirlerinin biyomoleküle bağlanma bölgelerinin ve bağlanma oranlarının direkt belirlenebilmesi amacıyla MALDI-MS/MS yöntemi kullanılmıştır. İnsülinin kullanıldığı büyük yapılı hibrit moleküllerin karakterizasyonu için parçadan-bütüne (bottom-up) proteomik analiz yaklaşımına gidilmiş ve daha sonra MALDI-MS/MS yöntemi ile PEG zincirlerinin bağlanma bölgeleri ve oranları belirlenmiştir. Bu tez çalışması sonucunda, PEG zincirlerinin uç grupları farklı şekillerde modifiye edilebilmiş ve bu PEG zincirleri kullanılarak yapılan konjugasyon reaksiyonlarının başarılı bir şekilde gerçekleştirildiği MALDI-MS yöntemi kullanılarak belirlenmiştir. PEG zincirlerinin biyomolekül üzerindeki bağlanma bölgelerinin yeri ve oranının belirlenmesi, tez kapsamında geliştirilen örnek hazırlama ve MALDI-MS/MS analiz yöntemleri ile pratik ve hızlı bir şekilde gerçekleştirilmiştir.
EPDM elastomerlerinin gerilme durulma davranışlarını kontrol eden parametrelerin belirlenmesi
Bu çalışmanın temel amacı dinamik uygulamalar için yeni nesil EPDM elastomerler kullanılarak yüksek sıcaklıklara karşı performansın arttırılması ve bu EPDM elastomerlere katkı maddelerinin etkisinin aydınlatılmasıdır. Bu amaçla geleneksel EPDM (EPDM-0) ve yeni nesil EPDM (EPDM-A) olarak adlandırılan yüksek molekül ağırlığı ve dar molekül ağırlığı dağılımına sahip yeni nesil EPDM'ler kullanılarak doğal kauçuk (NR60) ile karşılaştırılmıştır. Yeni nesil EPDM'lerin yağ etkisini karşılaştırmak amacı ile EPDM-A,EPDM-A5 (5 phr), EPDM-A10(10 phr), EPDM-A20(20 phr), EPDM-A30 (30 phr) elastomerleri hazırlanmıştır. Kükürt oranının etkisini incelemek için EPDM-AHS yüksek oranda kükürt içeren ve EPDM-ALS yani düşük oranda kükürt içeren karışımlar hazırlanmış ve karşılaştırılmıştır. Tez kapsamında öncelikle hazırlanan elastomerlerin evrensel test cihazıyla kopmadaki uzama ve kopma dayanımları tayin edilmiştir. %100 uzamadaki modül sonuçları incelendiğinde 1,88 MPa ile EPDM-A elastomerinin EPDM-0 ve doğal kauçuktsn hazırlanan NR60 elastomerine göre mekanik özelliklerinin daha iyi olduğu görülmüştür. Tezin ikinci aşamasında sıcaklık taramalı gerilme durulma (TSSR) cihazı ile durulma özellikleri incelenmiştir. TSSR sonuçları değerlendirildiğinde moleküler ağırlık dağılımına bağlı olarak izotermal gevşeme özelliklerinde değişiklikler meydana gelmiştir. Yeni nesil EPDM'lerde yağ içeriği arttıkça %50 gerdirmek için gerekli olan kuvvetin azaldığı izotermal gevşeme oranının da düştüğü görülmüştür. İzotermal olmayan sıcaklık taramalı gerilme durulma deney sonuçları değerlendirildiğinde sıcaklığın artmasıyla gerilim bölgesinde ikinci bir eğri oluşmuş ve bu eğri malzemenin kristallenmesi ile ilişkilendirerek tavlama deneyleri yapılmıştır. Yapılan tavlamaların sonucunda tavlama sayısı arttıkça servis sıcaklığında artış gözlemlenmiştir. Tez çalışmasının son aşamasında evrensel test cihazı kullanılarak sıkıştırma testleri yapılmış, doğal kauçuk ve EPDM elastomerlerin sönümleme özelliklerine bakılmıştır. Sıkıştırma testleri sonucu incelendiğinde EPDM-0 ve NR60 örneklerindeki %10 oranında sıkıştırılması durumunda absorblanan enerji değeri 23 mJ/cm3 değeriyle birbirine çok yakın kalırken EPDM-A'nın %10 basmadaki absorblanan enerji değeri 19 mJ/cm3 olarak EPDM-0 ve NR60'ın absorblanan enerji değerinin altında kalmıştır. Bu sonuçlar EPDM-A'nın dar moleküler ağırlık dağılımına ve yüksek çapraz bağ yoğunluğuna sahip olması ile ilişkilendirilmiştir. Tüm bu yapılan çalışmalar değerlendirildiğinde yeni nesil EPDM'lerin (EPDM-A) mekanik özellikleri artış göstererek dinamik uygulamalarda etkin şekilde kullanılabileceği görülmüştür.
Synthesis of poly(vinylpyrrolidone) (PVP) grafted silica as matrix for generation of palladium nanoparticles and investigation of effect of graft lengths on catalytic activity
The rationale of M.S thesis work is to investigate the effect of chain length of the stabilizing polymer brushes attached to silica surface on the formation of metallic palladium nanoparticles (NPs) and their catalytic activity. Poly(vinyl pyrrolidone) (PVP) brushes forming a very thin shell was grafted from silica microparticles (Si@PVP) via RAFT mediated graft polymerization method thus controlling the molecular weights and structures of PVP grafts. Palladium (Pd) nanoparticles were formed in PVP stabilizing matrix by gamma radiolysis of Pd(Ⅱ) ions to yield Pd(0) decorated core-shell particles (Si@PVP-PdNP). Size Exclusion Chromatography (SEC) and Thermogravimetric Analysis (TGA) results indicated the formation of PVP brushes with different molecular weights on silica. Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) measurements revealed that increased molecular weight of PVP brushes sterically blocked the particle growth and yielded more small Pd nanoparticles rather than fewer large ones. Si@PVP-PdNP having different PVP lengths and Pd sizes were evaluated for their catalytic activity and reusability in the model reduction of 4-nitrophenol to 4-aminophenol. It has been found that longer grafts are more effective in preventing NPs from leaking into the solution through the PVP shell, even if nanoparticles (NPs) are smaller in their presence, yet they allow the diffusion of reactants, resulting in more stable catalytic activity in repeated measurement cycles. On the other hand, short grafts are not sufficiently effective in preventing NP agglomeration and leakage. These findings are particularly important for heterogeneous catalyst systems in that they show the effects of surface-bound polymeric stabilizers on NP formation and catalytic activity.
Kozmetik endüstrisinde kullanılan bazı polimerlerin nano ölçekli yapı özellik ilişkilerinin araştırılması
Bu tez çalışmasında, günlük yaşantımızda sıklıkla kullanılan, yapılarında polimer içeren kozmetik ürünlerinden üç tip sıvı fondöten/krem (QW, LF ve BB krem kodlu örnekler) ile dört tip (farklı özellikleri olan sabitleyici/şekillendirici) saç spreyi üzerine odaklanılmıştır. Öncelikli olarak, kozmetik ürünlerde yaygın kullanılan beş farklı polimer belirlenmiş ve bu polimerlerin arasından (hacimsel) nano ölçekli oluşumlara yol açabilen polimetilsilseskuiokzan, polifenilsilseskuiokzan, feniltrimetikon, C 26-28 alkil dimetikon ve silikon elastomer reçine jel ile çalışmalar başlatılmıştır. Yapılan öncü çalışmalarda, bu polimerlerin nano ölçekli SAXS (Küçük Açı X-Işını Saçılması) analizleri yapısal değişimleri izlemede yol gösterici olmuştur. Saf polimerlerin kozmetik ürünlerde kullanım öncesi, yapı formlarında mevcut olan nano oluşumlarının morfolojileri (şekillenimleri), boyut bilgileri (jirasyon yarıçapları ve maksimum büyüklükleri) ile uzaklık dağılım fonksiyonları elde edilerek, 3B nano oluşumlarının ab-initio yapı modellemeleri yapılmıştır. İncelenen polimerlerden, küresele en yakın şekillenime sahip olan polimetilsilseskuiokzan (PMSQ), nano ölçekli yapı-özellik araştırmaları ile ilgili ayrıntılı çalışmalarda kullanılmak üzere seçilmiştir. Bu polimerin kozmetik kremlerin yapısal özellikleri üzerindeki etkisini incelemek üzere, iki farklı fondötene ve BB kreme farklı polimer katkılarında incelemeler yapabilmek üzere, 343 mg örnek için 0,4; 0,7 ve 1,2 mg (sırası ile % 0,12; 0,20 ve 0,35 kütlece katkı olacak şekilde) PMSQ eklenmiştir. PMSQ'nun diğer polimerlere göre tercih edilmesinin bir başka nedeni de, jel/krem formunda olan kozmetik malzemelerin içinde, bu polimerin makroskopik görüntüyü ve homojen yapıyı bozmayacak şekilde mevcut yapıda çözünerek, miktarının kolayca artırılabilmesi olmuştur. Polimer miktarı artırılarak ve artırılmadan (kontrol grubu olarak) hazırlanan örnekler X-ışını saçılma deseni oluşturmayan alt taşlar üzerine ve deri malzeme üzerine ince film formunda uygulanarak, bu malzemelerin SAXS ve WAXS (Küçük - Geniş Açı X-Işını Saçılması) analizleri yapılmıştır. Elde edilen SAXS (~1-100 nm ölçeğinde) ve WAXS (~1-3 Å ölçeğinde) verileri kullanarak yapısal incelemeler gerçekleştirilmiştir. Ayrıca bu örneklerin SEM ölçümleri de yapılarak, polimer miktarındaki artışının meydana getirdiği yapısal değişiklikler mikroskopik ölçekte de takip edilebilmiştir. Polimer katkılama artışına en iyi yanıtı veren LF kodlu fondöten ile BB krem kullanılarak hazırlanan film formundaki örnekler bu kez 1-4 hafta aralığında yaşlandırılmaya bırakılmış ve örneklerin SAXS analizleri Tayvan Ulusal Sinkrotron Işın Merkezi (NSRRC) de gerçekleştirilmiştir. SAXS analizleri ile elde edilen, nano oluşum uzaklık dağılım fonksiyonlarının, üç boyutlu yapılarda uzun erimlerde homojen dağılımın önemli bir göstergesi olduğu, SEM görüntülerinden elde edilen kısa erimli uzaklık dağılım fonksiyonlarına göre, çok daha doğru ve gerçekçi bulgular içerdiği de yarı-deneysel analizler ile gösterilmiştir. Bu aşamaya kadar yapılan analizlerde polimer artışına en elverişli olan yani, 3B nano morfolojilerin nanokompozit formuna uygun şekil, boyut ve uniform dağılım bilgileri veren, LF kodlu malzemeler olmuştur. Bundan sonraki analizlerde bu örnek üzerine yoğunlaşılarak, yapıları kontrol altına alınan polimer katkısındaki artışın yapı-özellik üzerine etkilerini incelemek üzere, antibakteriyel analizler ve UV soğurucu etkiler incelenmeye başlanmıştır. Sonuçta, film formundaki LF kodlu fondötenin artan PMSQ polimer katkısıyla antibakteriyel özelliklerinin geliştirilebildiği bulgusuna ulaşılmıştır. E.coli ve S.aureus bakterilerine ait artan polimer katkısı ile biyofilm oluşumunun önüne geçilebildiği belirlenmiştir. Ayrıca bu grup için UV optik geçirgenlik ve yansıtma ölçümleri de yapılmış ve 0,4 mg PMSQ katkılama ile elde edilen kozmetik malzemenin UV yansıtma özelliğinin ~% 15 artırıldığı , UV geçirgenlik özelliğinin ise ~% 40'lara kadar azaltılabildiği sonucuna ulaşılmıştır. Aynı örnek grubunun FT-IR analizleri de yapılmış ve PMSQ miktarındaki artış ile moleküller ölçekte yapılarda değişimlerin olup olmadığı da incelenmiştir. İkinci kozmetik ürün grubu olarak, farklı özelliklere sahip dört saç spreyi ile çalışılmıştır. Bu spreyler, 25-35 yaş grubu bayan donörlerden alınan farklı (düz sarı, düz kumral, düz siyah ve kıvırcık kahverengi) formlardaki saç örnekleri üzerine uygulanmış ve yapısal analizler SAXS yöntemi ile başlatılmıştır. Nano oluşum morfolojileri küresele en yakın olan "düz sarı" ve "düz kumral" saç örneklerine moleküler yapı farklılıklarını incelemek üzere FT-IR analizleri de yapılmıştır. Mikroskopik analizler ise SEM (Taramalı Elektron Mikroskopisi) ve EDXS (Enerji Dispersiv X-Işınları Spektroskopisi) yöntemleri ile tamamlanmıştır. Bu grup için elde edilen en önemli bulgu şu şekilde özetlenebilir. Saç spreylerinde kullanılan kimyasal bileşenler, işlevlerini gerçekleştirirken saçın moleküler yapısında çok büyük değişiklik oluşturmamasına rağmen, nanoskopik yapısında (özellikle melanin yapıda) büyük değişikliklere yol açabilmiştir. Bu bulgu, nanoskopik analizlerin kozmetik endüstrisinde mutlaka kullanılması gerekliliğinin bir göstergesidir. Bu tez çalışması ile ilk kez belirlendiği üzere, SAXS analizleri ile elde edilen 3B ab-initio yapı modellemeleri melanin yapıyı izlemede rahatlıkla kullanılabilir. Bu çalışma ile ilk kez SAXS yöntemi ile, saçın yapısında mevcut olan melanin (nanoglobular) formlarının doğal ortamlarında 3B modellemeleri yapılabilmiştir. Kozmetik ürünlerde yaygın olarak kullanılan polimerlerin ve diğer makromoleküler yapıların bir araya gelmesi ile nano ölçekte ortaya çıkan nano oluşumların kendiliğinden (self-assembled) düzenlenmesi ile yapı-özellik ilişkilerinde çok farklı sonuçlar ortaya çıkabilmektedir. Yani kozmetik endüstrisinde nano ölçekte ciddi yapı kontrollerinin yapılması çok yerinde olacaktır. Bu çalışma kapsamında, polimer kullanım oranlarındaki küçük değişikliklerin bile, nanoskopik yapı farklılıklarına yol açtığı, bu nano ölçekli yapısal farklılıkların da antibakteriyel özellikleri geliştirmesi ve UV koruyucu kalkan etkisini artırması gibi, biyofiziksel özelliklerde de etkili olduğu ortaya çıkarılmıştır. Özetle, bu tez çalışması sonucunda, kozmetik endüstrisinde polimer malzemelerin kullanımının optimum oranlarda belirlenmesinin gerekliliği ve yapı-özellik ilişkilerinin moleküler boyuttan başlayarak nano, mikro ve makro boyuta kadar daha ciddi biçimde incelenmesi gerekliliği açıklanmıştır.
Computational and experimental approaches to develop doxycycline imprinted hydrogels for contact lenses
The aim of this thesis is to develop drug delivery hydrogels for contact lens applications which are used as therapeutic agents for cronic diseases such as high eye pressure, cornea neovascularization, eye dryness etc. Contact lenses are optical instruments which are used for elimination of visual defect or cosmetical and therapeutical purposes. Nowadays, contact lenses are made by hydrogel materials which has high water cater content and biocompatibility due to chemical properties. In the studies, newly developed contact lenses are intended to be used for the treatment of ophthalmological diseases. Drug molecules can be loaded to the contact lenses with various methods such as soaking, molecular imprinting or loading to the polymer matrices with colloidal nonoparticles. In this study, doxycycline hyclate molecules are loaded to the hydrogels by soaking and molecular imprinting methods. In this thesis, molecular imprinting method was preferred to synthesize controlled drug released hydrogels. Imprinted polymers which have special cavities belonged to target molecules, are highly selective against to targets. In this study, doxycycline hyclate molecule is choosen as target molecule which is imprinted to the hydrogel matrices. Doxycycline hyclate which is broad spectrum antibiotic, has not been used as template molecule for contact lens applications in literature. In this study, computational methods were used to select suitable monomers for doxycycline imprinted hydrogel synthesis. In molecular simulation step, quantum mechanics, molecular mechanics and molecular dynamic techniques were used. By using quantum mechanics and molecular mechanics, binding interactions between functional monomers and doxycycline molecule were calculated. Quantum mechanics calculations were carried out with Gaussian 09 and SYBYL-X software was used for molecular mechanics studies. Molecular dynamic studies of functional monomer-doxycycline systems were carried with Material Studio 5.0. Also, the effects of crosslinker on prepolymerization step were investigated with molecular dynamic studies. In this step, interactions of crosslinker-doxycycline-functional monomer were studied to simulate experimental conditions. These results were compared with experimental results. In the experimental part, in order to determine crosslinker effect on drug release performance, doxycycline hyclate imprinted and non-imprinted hydrogels were prepared in various crosslinker ratios (1, 1.5, 2, 3 % mole EGDMA). Imprinted and non-imprinted hydrogels were syntesized by free radical polymerization. Acrylic acid was choosen as functional monomer for polymer synthesis. All hydrogels were characterized by Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). Also, swelling behaviors of hydrogels were investigated. Doxycycline loading and release performances of both imprinted and non-imprinted hydrogels were investigated. Based on release performances, drug release kinetic profiles were evaluated. According to loading and release performances, doxycycline imprinted hydrogel sample which include 3% mole EGDMA, has higher imprinting factor and more controlled drug release performance compared to other hydrogels.
Effects of polyhedral oligomeric silsesquioxane reinforced polypropylene (PP) nanocomposites on the thermal, mechanical, and optical properties of PP
Polymeric hybrids and nanocomposites containing polyhedral oligomeric silsesquioxanes (POSS) - general formula (RSiO1.5)n where R is an organic group – as dispersed inorganic phase offer the opportunity to design advanced materials with enhanced thermal and mechanical performances. The incorporation of POSS or its derivatives into polymers can lead to some improved properties, such as the increase in use temperature, oxidation resistance, surface hardening and mechanical strengths, as well as reductions in flammability, heat evolution, and viscosity during processing. It has been pointed out that the morphology, the thermal stability and tensile properties of thermoplastics (polyolefins, polyesters, polyamides, etc.) containing POSS can be largely affected by the chemical structure, concentration and dispersion degree of POSS nanoparticles. It is possible to obtain dispersion of POSS particles to the scale of individual molecules with size approximately 1-2 nm. In view of this, POSS molecules are nearly equivalent in size to most polymer segments and, therefore, potentially can exert dramatic reinforcement effects. In contrast to other nanofillers, such as layered silicates which are platy and carbon nanotubes which are cylindrical, the shape of the POSS molecules is isotropic. In addition, POSS molecules can be easily functionalized by chemically altering the R groups. This presents opportunities for copolymerization or grafting reactions with functional groups on polymer chains and for defining and controlling the nature of interactions between POSS molecules and the polymer chains. Polypropylene (PP) is a versatile member of polyolefins and this thermoplastic polymer is used in a wide variety of applications including packaging, textiles, stationery, plastic parts and reusable containers of various types, laboratory equipment, loudspeakers and automotive components. PP has been used as the matrix material in a commercial form because of its many attractive properties, such as low weight, relatively low cost, excellent heat distortion temperature (above 100 °C) and its recycling ability. But its toughness, strength and stiffness are not sufficient for applications as an engineering plastic. To reinforce PP, polymer nanocomposite technique by adding rigid polymers, is used. In this study, 1, 3, 5, 8, 10 wt-% POSS containing PP nanocomposites PP/POSS nanocomposites (PP/POSS NC) were prepared by melt blending via extrusion. Methyl-POSS reinforced polypropylene (PP) nanocomposite was used as POSS carrier material (or as a masterbatch) and the effects of methyl-polyhedral oligomeric silsesquioxanes (methyl-POSS) on the rheological, and thermal behavior of polypropylene (PP) were investigated. Rheological studies of PP/POSS NC pellets were operated by using parallel plate rheometry at three different temperatures. For all samples, it can be observed that complex viscosity (η*) decreases with increasing frequency, both storage modulus (G') and loss modulus (G'') progressively increase with increasing frequency. Complex viscosity showed large increase with reduction of temperature at high frequency. The increase of frequency causes the restriction of chain movements and a stiffer behavior was observed. Thermal behaviors of nanocomposites were characterized by DSC and TGA. The fusion enthalpy of the nanocomposites (obtained by peak integration) decreases with increasing of POSS content. 5% and 10% weight loss temperatures obtained from TGA curves. It was observed that increasing of POSS content increased these degredation temperatures and also the thermal stability of nanocomposites. The prepared PP/POSS nanocomposites and PP pellets were also subjected to melt spinning process by using capillary rheometer with 6 take up speed and 3 plunger speed to produce 97 fiber samples. Draw down ratio (DDR=Ddie2/Dfiber2) of fibers were calculated and the effects of draw down ratio on the strength, and polymer chain orientation were investigated by mechanically, optically and morphologically. Mechanical properties of prepared fiber samples measured by universal testing machine. It was observed that POSS composition and DDR of the nanocomposites had a pronounced effect on the tensile properties of these materials. Tensile data shows that the modulus increase with increasing of take up speed and decreasing by increasing of POSS content. Addionally, the maximum load, tensile strain at maximum load, and tensile strain at break decreases with increasing of take up speed. Morphological characterizations were made by using polarized optical microscope (POM) and small angle X-ray scattering (SAXS). Birefringence data of fibers calculated by using POM images and DDR of samples. For all fibers, increasing of DDR lead to increase birefringence. The other result was that increasing of POSS content caused the decrease of birefringence values with the comparison of neat PP. SAXS pattern clearly showed that isotropy of fibers increases with increasing of POSS content. On the other side, increasing of take up speed increases anisotropy. Increasing of take up speed also increased the fiber orientation. Furthermore, it was observed that high POSS content fibers have more isotropic structure. In consideration of this observation it is clearly seen that POSS content effects the morphology of fibers significantly.
Statistical mixture design of experiment studies for UV curable coating formulations for acrylonitrile butadiene styrene (ABS) substrates
This thesis was studied in cooperation of Arçelik A.Ş. to fulfill the goal of developing high stratch resistance, environment friendly, water-borne, UV curable, transparent coating formulation for Acrylonitrile butadiene styrene (ABS) surfaces. ABS and Polycarbonate/acyrlonitrile butadiene styrene (PC/ABS) is used for plastic parts of the small home appliances as an example top covers of coffe machines and dishwashers in Arçelik A.Ş. and its stratch resistance is very low (0,1 N) like the most of all plastics as well. Therefore it can be stratched easily and lost their appealing, gloss appearance in a short time. This issue cause to displeasure and complaints of customers decrasing the preferability of the products between the other brands. Two different solution can be offered for this problem. It might be added some additives to increase the stratch resistance of plastics which is a harder way. On the other hand, high stratch resistance coating formulation can be developed as a more practical solution. In Arçelik A.Ş., different kind of functional coatings are used for good appearance (gloss, colour), corrosion-protection, anti-finger and easy to clean surfaces. However, currently all kind of coatings which are used in Arçelik, are cured thermally. These thermally cured coatings are not energy-saving because of their high curing temperature and long curing time. In contrast UV-curable of coatings are energy-saving with their application in ambient curing temperatures in addition, it provide to able to cure temperature-sensitive substrates like plastics. The other superior property over the themal curing system is obtaining higher stratch resistance and gloss coatings using UV curing systems. Considering of these advantages of UV-curable coatings, this thesis study objected to developing coating formulation and applying the formulation to ABS surfaces using in products in Arçelik and UV curing of it. As it is know, it is not meaningful to obtain high stratch resistance coating but it is not adhesive to substrate with a long-time durability. Therefore adhesion to surface is the most significant issue to overcome. To ensure for quality, coatings are tested by different test methods according the Arçelik quality requirements for stratch resistance aiming to increase 0.1 N to 3 N, 100% adhesion to surface and their durability against to different chemical and physical effects.
Effects of anionic surfactants on styrene-acrylic copolymer emulsion for wood coatings
Wood coatings have the biggest share in industrial coatings market. Because of high VOC content of conventional solvent-based systems, the market share of low-VOC systems are increasing year by year. Because of the low cost and ease of application of water- based 1K acrylic emulsion systems, they have the biggest increase within low-VOC systems. Water-based 1K acrylic systems differentiate in terms of their end use application and application method. It is convenient for brush, spray, curtain or roller coater systems. It has a wide range of application like furniture, exterior wood substrates, floors, industrial mdf panels, etc. From chemical point of view, styrene-acrylic copolymers, pure acrylic copolymers or vinyl acrylic copolymers can be used in several wood coating application. Main performance criterias are hardness, early hardness development, sandability of the film, scratching resistance, drying time, blocking resistance, chemical resistance and asthetistical properties. The aim of this study is to examine how a range of different anionic surfactants affect the polymerization of styrene-acrylic emulsion and the end properties of an interior clear wood coating system prepared with these copolymers. The surfactants used in this study include different types of anionic surfactants as sodium lauryl suphate, sodium lauryl ether sulphate (2EO and 4EO), sodiım dodecylbenzene sulphonate, alkyl polyethylene glycol ether sulphate, polyoxyhethylene tridceyl phospate ester and disodium exthoxylated alcohol [C10-C12] half ester of sulfosuccinic acid.
ATRP ile bor içeren polimetilmetakrilat sentezi
In this study first of all two different initiators were created and then these two initiators were used in ATRP reaction effectively. Hydroxyl groups were changed with active bromide group with the help of. 2-bromopropionyl bromide that are take part in Carboranemonool and carboranediol structures. FT-IR and NMR methods were used for characterization of initiators.Carborane initiators were used for polymerization of methylmethacrylate.Mainly the effect of reaction time was examined onto the polymerization.Conversions of polymers were determined gravimetrically.Gel permeation chromotography (GPC) was used to determine molecular weight of all polymers,Differential scanning calorimetry (DSC),were used to determine Tg values of all polymers Thermogravimetric analyser (TGA) were used to determine 50% percent degradation time and char yield amount of polymers at 500 oC and 800 oC.These methods were used for characterization of all polymers
Synthesis of styrene-acrylic copolymers and their use in paint
In this study, different types of silanes, which have different structures, are added directly to the styrene-acrylic copolymers. These copolymers are formulated in high PVC paint formulation. These paints are tested in according to their scrub resistance, hardness and flexibility properties.
Investigation of effect of bitumen chemical composition, polymer and warm mix asphalt additives on the properties of bitumen by using response surface method
Bitumen, a binder material used in asphalt applications, is one of the important components that affects the service-life of asphalt. Bitumen chemistry, and amounts of Saturate, Aromatic, Resin, Asphaltene (SARA) fractions within the bitumen, affect the properties of both base and modified bitumen. The desired properties of bitumen change with varying content of bitumen and purpose of application. To improve the properties and the performance while using in the asphalt mixtures usually the polymer addition is utilized. While thermoplastic elastomers are mostly preferred, plastomers such as polypropylene, ethylene vinyl acetate, and natural / synthetic rubber can also be used for the modification of bitumen. The addition of materials like Styrene-Butadien-Styrene (SBS) copolymer can simultaneously develop the durability and flexibility at high temperatures by containing the both soft and hard segments in its structure. In addition, hot mix asphalt additives can be used to prepare bitumen-aggregate mixtures at lower temperatures in order to improve the application conditions. For this purpose, organic or chemical additives included into the bitumen, as well as processes with the foaming techniques can be used for lowering the mixing and layout temperatures. Influence of all these additives on the properties of bitumen changes with the type and amount of additive and bitumen chemistry. An additive applied to improve the some properties of bitumen may adversely affect another feature of the bitumen and consequently asphalt. Especially when the addition of these additives together and variety in the bitumen chemistry are taken into consideration, the desired properties may not be obtained in the final product. Therefore, understanding the simultaneous effect of the variation of bitumen composition, amount of polymer and warm mix additive on the bitumen properties is aimed in this study. Experimental statistical methods were used for this purpose and the effects of independent parameters on the response functions individually and simultaneously were investigated by using Response Surface Method. The composition of bitumen and the amount of polymer and warm mix asphalt additives were defined as independent variables in this study. Dynamic shear rheometer (DSR), Bending beam rheometer (BBR), Elastic recovery and Viscosity were determined as response functions of this system. The effects of these independent variables on the response functions were investigated by the full factorial analysis initially and then the response surface method. In the experimental study, SARA analysis was performed on the bitumens which are in the same penetration grade and obtained from Izmit, İzmir and Batman refineries. Furthermore, Fourier Transform Infrared Spectroscopy (FTIR), Simulated Distillation Gas Chromatography (GC-SimDis), Differential Scanning Calorimetry (DSC) and Thermal Gravimetric Analysis (TGA) were performed for detailed characterization of the bitumens. Styrene-Butadiene-Styrene (SBS) tri-block copolymer and a commercial paraffin wax were used as warm mix asphalt additives for the modifications of the bitumens. FTIR, DSC and TGA analysis were carried out to determine whether these additives can be used in bitumen blends. When the results of characterization tests and chemistry of bitumen were considered together, it can be seen that the same penetration grade bitumens may have different chemical properties and when the performance grade was determined according to TS EN 14023 standardization it may be also found different. This result shows that it cannot be achieved same performance grade by applying the same modifications to the same penetration grade bitumens which have different chemical compositions. Moreover the difference of SARA fractions in the three bitumens could not be seen in the FTIR analysis. The reason for the lower initial boiling point observed in GC-Simdis and the low temperatures at which loss of mass starts for Batman bitumen in TGA analysis are due to the light fractions of the Batman bitumen rather than the amount of saturated content. On the other hand, the high amount of aromatic and saturated structures in the bitumen decreased the glass transition temperature of Izmit bitumen. For the characterization analysis of the additives, it has been proved that the properties of the additives are the same as those of the commercially available common ones having without extra features. The Gaestel index (GI), one of the independent parameters, was used to define the bitumen chemistry in a single variable and examine the effect of bitumen chemistry on the response functions. The GI values of İzmit, İzmir and Batman bitumens were calculated by using the determined SARA fractions as 0.487, 0.622 and 0.988, respectively. In the experimental design matrix, 3 discrete values (0.487, 0.622, 0.988) were defined for the GI as discrete numeric variable, and 2-5%, 1-3% upper and lower limit values for the SBS and Wax, respectively, which were defined as continuous variables. Within these limits, bitumen modifications were made according to the experimental matrix designed by JMP® software and DSR, Viscosity, Elastic recovery and BBR tests which were determined as response functions of system, were carried out. Model equations were constructed with response functions of independent variables by using the data obtained from the measurements and the response surface method. Three-dimensional response surfaces and two-dimensional interaction curves are plotted by using the model data that indicates the effect of each parameter on the properties of bitumen. For the individual analysis, all independent variables were found as significant in different degrees for DSR and BBR response functions. The increasing amount of SBS promotes the value of DSR and creep stiffness exponentially. However this increasing trend affects the creep stiffness negatively since it has the upper limit in the standard. Furthermore the bitumen composition which was defined as GI in the analysis, was an effective term on the all response functions especially for elastic recovery, viscosity and DSR properties which improve rapidly with the increasing value of GI. The higher amount of asphaltene and saturates or lower amount of resins and aromatics enhance the higher value of GI. On the other hand, the amount of wax were determined as insignificant on the viscosity and elastic recovery properties of bitumen despite the fact that the wax is known as an organic additive for viscosity decreasing in the asphalt mixtures. This may be the result of the fact that the viscosity decreasing effect of Wax is very small, comparing with the increasing effect of the SBS and GI. Finally, the optimum values of variables were determined by performing the simultaneous analysis of independent variables with the four response functions together within the desired performance limits. The optimization analysis showed that all variables have effects on the response functions in different degrees. When the result of simultaneous analysis of response functions were compared to the individual analysis, there were terms added or eliminated from the model expression. Especially the GI*GI term which is important for the effect of bitumen composition on the response function was found as insignificant for DSR, Viscosity and Elastic recovery responses in simultaneous analysis. The reason for this was shown as the given limitation for the maximization of DSR and Elastic recovery and the minimization of viscosity. The optimum variable values within the given response limits are GI: 0.988, SBS: 3.2% and Wax: 3%. Tests within the scope of EN 14023 standard and asphalt tests were carried out on modified bitumen prepared in optimum values to investigate the improvement on the performance on both bitumen and asphalt properties. The performance grade of neat Batman bitumen was found to be PG 70-22 while it was determined as PG 82-16 after the modification at optimum conditions. As a result of the modification, while the high temperature performance of bitumen improves as two performance grade, the low temperature performance was affected negatively. The reason maybe that all the modified bitumen samples has the result on BBR as -16 since the addition of SBS increases the creep stiffness and although the amount of SBS is minimum (%2), the performance criterion was not achieved on -22. As a result of the Marshall asphalt design for determining the asphalt properties, aggregate-bitumen blends had 4.8% of the unmodified bitumen, whereas it was necessary to use 6.2% of the modified bitumen. Asphalt samples prepared by using the amounts of bitumen found in design and tested on the wheel tracking test machine. The amount of rutting were found as 13% for unmodified bitumen, while in the modified bitumen this value was improved by 50% to 6.7%. Thus, the DSR, viscosity, elastic recovery and creep stiffness properties of the bitumen have been successfully modelled based on the bitumen content, amount of polymer and warm mix asphalt additives and optimum mixing ratios have been successfully determined by using the "Response Surface Method". The widespread use of experimental design methods will provide a scientific and realistic basis for the preparation of asphalt mixture formulations instead of personal experience as well as the prevention of waste of time.
Grafting of poly(acrylamide) onto crosslinked poly(HEMA-co-MMA) resin for removal of phenol and bisphenol A
Phenol and its substituted derivatives are widely found in the effluents from pesticides, synthetic rubber, plastic, pharmaceuticals, petrochemicals, and other industries. It is also used in the production of caprolactam and bisphenol A. They are intermediates in the manufacture of nylon and epoxy resins, respectively. It is primarily used in the production of phenolic resins, which are needed in the automotive plywood, construction and appliance industries. Other important uses of phenol are as a disinfectant and in medicinal products. Minor uses of phenol contain the manufacture of paint and varnish removers, lacquers, paints, rubber, ink, illuminating gases, tanning dyes, perfumes, soaps and toys Phenol and phenolic compounds are generally considered as one of the important organic pollutants discharged into the environment causing unpleasant taste and odor of drinking water. Even at very low concentrations in the presence of water, is undesirable and toxic to the aquatic beings including fish. Especially, chlorinated phenols are more toxic to aquatic life. Phenols have great risk to the human health and cause negative effects on the brain, digestive system, heart, eye, liver, kidney, lung, peripheral nerve, skin and the unborn child. 0.002 mg L-1 is the permissible limit for phenol concentration in potable water according to the World Health Organization regulation. Removal of phenolic pollutants in aqueous solutions can be divided into three main categories: chemical, physical and biological treatment. Several wastewater treatment methods for removal of phenolic pollutants have been used including membrane filtration, advanced oxidation, biological degradation, photocatalytic degradation, electrochemical oxidation and adsorption. Adsorpsion is very important method to remove organic and inorganic pollutants. Different adsorbents such as zeolites, carbon nanotubes, polymeric sorbents and clay have been investigated for the removal of phenol and phenolic pollutants from wastewater. Three mechanisms of phenolic compounds adsorption is postulated namely, π-π dispersion interaction, electron-donor acceptor complex formation and hydrogen bond formation. This methodology was used to prepare new polymeric sorbents for phenol removal. In this thesis, two types of polymeric sorbents were prepared for removal of phenol and BPA from water. The poly(HEMA-MMA-EGDMA) terpolymer were prepared by using suspension polymerization method starting from polymerization of hydroxyethyl methacrylate (HEMA) (50%), methyl methacrylate (MMA) (40%) and ethylene glycol dimethacrylate (EGDMA) (10%) as crosslinkerin the presence of toluene as porogen and AIBN as an initiator (resin 1). Other polymeric resin was prepared grafting polymerization of poly (acrylamide) onto resin 1 by redox polymerization method. Grafting reaction is carried out through the hydroxyl groups on HEMA units. The resulting polymer resin2 , which had a total nitrogen content of about 7.0 mmol/g, was effective in extracting phenol from aqueous solutions.The phenol and BPA sorption capacities were found depending on concentration and pH. Also, phenol and BPA sorption kinetics of the resins were investigated. Kinetic models were applied for Resin 1 and Resin 2.
Synthesis of bio based polyurethane surface coating materials and characterization
During the last few years, there is a continuous search of advanced polymeric materials for coating applications. Polyurethane resins are a class of thermosetting polymer materials largely used in high performance surface coatings and paints. Fast depletion of petroleum stock and increase in their cost puts limit to their use in future for production of petroleum-based resins. Renewable resources used in the preparation of polymers are falling in the class of biomaterials which are rich in hydrocarbons and most of the times obtained from parts of profusely available agriculture feed stock. The current oil based polymers are prepared by consuming petroleum based anhydrides and dicarboxylic acids. Use of non-edible vegetable oils and their fatty acids are currently the raw materials focused in synthesizing polymeric materials as renewable sources due to increasing economic and environmental concerns of petroleums. Polyurethanes have found many applications starting from coating, paint, foam, thermosetting, thermoplastic elastomer to fiber. However, their relatively low abrasion and wear resistance and environmental degradation, limit their application in surface coating. In the past decade, nanostructure organic-inorganic composites based on organic polymer and inorganic materials have attracted great interest of researchers.These composites exhibit the enhanced performance properties compared to conventional composites because of the maximized interfacial contact between the organic and inorganic phases. So, proper design of polyurethane with appropriate structure and composition of the components may result unique and useful properties for its different end applications. In the present work we have attempted to utilize the castor oil for the synthesis of biopolyurethane coating material. The double bonds in triglycerides are not active enough to take part in free radical polymerization reaction generally. Maleation is a method to increase crosslink density of the final polymer thanks to reactive maleate double bonds. To convert maleated oils into polyols, it was first epoxidized. Hydroxylation of castor oil was carried out with hydrogen peroxide. It was further reacted with different isocyanates in different ratios to develop a series of biopolyurethanes. The synthesized polyurethanes were characterized for the evaluation of their chemical and thermal properties and the effect of isocyanates loading into polyurethane on these properties are also being presented. The thermal properties of biopolyurethane coating materials were studied using thermo gravimetric analysis (TGA). The effect of NCO/OH molar ratio on thermal and mechanical properties of coatings was studied for the prepared biopolyurethane coatings.
Influence of water-cement, polymer-cement and fiber-cement ratios on properties of fiber reinfroced mortars
Mortars are one of the very important construction material to build safe buildings, bridges, barrages and new constructions. Because of its importance and its huge usage area, they are frequently researched by universities and by firms. There is also need for further modification and analysis of mortars to develop this material for future applications and according to needs of humans. This study focuses on influence of different ratios of water-cement, polymer-cement and fiber-cement ratios, hybrid fibers on mortars. Due to this aim a mathematical model is evaluated. To create mathematical model surface respond method has been used. As a design of experiment, central composite design has been used. Fiber type and polymer type are selected constant during mathematical model. Only 12mm glass fiber and acrylic-styrene copolymer resin has been used. The proportions of polymer-cement, fiber-cement and water-cement ratios are evaluated according to central composite design. There is an important advantage to use surface respond method in the experiments. In the end of experiments, the results can be defined as mathematical equations and it is possible to estimate the whole results in the range of design of experiments without making further experiments for unselected values. Out of mathematical model, there are three group of polymer modified hybrid fibered mortar produced. In hybrid fibered mortars combination of polypropylene-12 mm glass fiber, polyamide-12 mm glass fiber and 3mm Cem-FIL glass fiber are evaluated. Additionally, one group has been produced with 6mm surface treated glass fiber. To find out the trade-off between effect of polymers, different type of and different amount of fibers and also the effect of combination of fibers, flexural, compressive and slump tests are performed. Slump tests are performed after the mixing of fresh mortar. Due to using slump values, viscosity and processability of mortar have been understand. After production of mortar specimens, they are waited 2 days in water pool and totally 60 days are waited. Because of the polymer content, the cure time is restricted to 2 days. After production, after water cure and before testing the specimens, their weight are calculated and noted to see their weight change up to time. The magnitude of specimens are 40x40x160mm3. There are totally 60 specimens according to mathematical model, 9 with hybrid fibered and 3 with surface treated fibered mortar specimens produced. Extensive results of mechanical, weight-loss and viscosity of mortars is discussed in result and discussion part.
Evaluation of silicone polymers in shampoos
Being one of the industries which is least effected by various economic crisis in the world, personal care industry is known with its wide range of products and dynamic consumers. Among all personal care products, shampoos are known to be of interest by all consumers of all age groups since shampoos are perceived by the consumer as the "must-have" items. Silicones are used in a number of personal care products, providing their unique sensory benefits from shampoos and skin creams to cosmetics and antiperspirants. Silicones are fast becoming an essential ingredient in the cosmetics and personal care market as producers continue to provide more customized and specialized silicone ingredients to meet consumer demand for innovative, multifunctional and sensory-appealing products. Clear shampoos are perceived as being pure and less harmful to both hair and skin by consumers, as they do not weigh down hair, provide volumizing and contain less amount of ingredients. Thus, main aim of this study was to formulate a clear and conditioning shampoo while investigating the behaviors of silicones in shampoo base. Moreover, the shampoo industry is moving towards using less amount of ingredients and obtaining optimum results. Functional silicones play a critical role on the overall effect of such shampoos because functional silicones can provide ease of combing, shine, volume and enhanced foam. In this study, different types of silicones were investigated in shampoo systems. These silicones are graft silicone copolymers, trisiloxane polyethers and finally polyetheramine silicone copolymers. The aim of the study was to see which silicone system can be thickened by salt, what kind of effect the stable formulations provide on hair, the solubility profile of the silicones in shampoo system, to see clarity and uniformity of the finished products. The most successful formulations were obtained in Experiment 5 and 6. The results of experiment 6 were by far the optimum results in terms of conditioning both for hair and skin. Sodium Laureth Sulfate and Cocamidopropyl Betaine are selected as the surfactants. Methyl Gluceth-20 and C12-15 Alkyl Lactate are used as thickeners in selected formulations. Shampoos were evaluated for clarity, viscosity, salt (NaCl) content/efficacy and via combing force, conditioning effect, shine and conditioning properties of the applied hair. Emulsion silicones were found to provide conditioning, ease of combing and softness to both wet and dry hair and as well as skin. The final formulations with the emulsion silicones can also be used in facial washes, body washes, shower gels and hand washes by doing slight changes in formulations. These formulations can also be opacified by using glycol distearate and/or acrylates copolymer based opacifiers/thickeners.
Antibacterial amphiphilic polymers based on enzymatically synthesized polycaprolactone
Amphiphilic polycaprolactone (PCL) based polymers were synthesized utilizing three different approaches including the combination of enzymatic ring-opening polymerization (eROP) either with photopolymerization and atom transfer radical polymerization (ATRP). The side reactions during the synthesis of methacrylate initiated eROP of ɛ-caprolactone (CL) was scrutinized to reveal the formation of different end-groups. Effect of reaction time initiator/lactone ratio and the synergetic effect of temperature and initiator/lactone ratio as 2-hydroxyethyl methacrylate (HEMA) was the nucleophilic initiator, Novozyme-435 (N435) was the immobilized lipase catalyst. α,ω-methacrylated PCL macromonomer was synthesized to have the benefit of the side reactions investigated at the first place, utilizing ethylene glycol dimethacrylate (EGDMA). Since, water acted as the nucleophilic initiator in the beginning of the reaction, EGDMA was degraded by N435 and tailored onto the ends of the PCL chains resulting in mixture of macromonomers comprising a combination of methacrylate, HEMA, and hydroxyl end-groups together with ethylene glycol (EG) moieties along the chain. The mixture of PCL chains were concisely called as dimethacrylated PCL or α,ω-methacrylated PCL (DMPCL). DMPCL was employed as a long crosslinking agent in the photopolymerizaton of poly(ethylene glycol) methyl ether methacrylate-950 (PEGMA-950) with the aid of trimethylolpropane triacrylate (TMPTA) and Irgacure-819 as the initiator under light emitting diod (LED) ultraviolet (UV) bulbs. To achieve amphiphilic copolymer of PCL and poly(ethylene glycol) (PEG) with another strategy, a macrophotoinitiator based on PCL was again synthesized via eROP when Irgacure-2959 was used as the nucleophilic initiator. Light-induced polymerization was again applied to reach PCL copolymers with butyl acrylate (BuA), benzyl acrylate (BzA), tetrahydrofurfuryl acrylate (THFA), 2,2,2-trifluoroethyl acrylate (TFEA), 2-hydroxyethyl acrylate (HEA) and poly(ethylene glycol) methyl ether acrylate-480 (PEGMEA-480). PEGMEA-480 and sulfobetaine methacrylate (SBMA) were also installed on enzymatically synthesized PCL to achieve AB and ABC type block copolymers via ATRP. Following the end-functionalization of enzymatically synthesized PCL with 2-bromoisobutyryl bromide, diblock copolymer of P(CL)n-b-P(PEGMEA)m and triblock copolymer of P(CL)n-b¬-P(PEGMEA)m-b-P(SMBA)k were achieved. The structures of the abovementioned polymers were analysed with 1H nuclear magnetic resonance (NMR), fourier transform infrared spectroscopy-attenuated total reflection (FTIR-ATR), differential scanning calorimetry (DSC) and size exclusion chromatography (SEC). The antibacterial properties of the polymers were investigated via zone inhibition test method. The side reactions during the synthesis of methacrylate initiated enzymatic ring-opening polymerization of ɛ-caprolactone (CL) was scrutinized. It was revealed that N435 has high activity enough to catalyze enzyme-monomer complex formation, initiation, and propagation, cleaving the ester bond of the hydroxyl bearing acrylate initiator at the same time. Therefore, it was revealed that it might be preferable to study at lower reaction temperatures to reduce the side reactions inside the sufficient activity range of N435 or other lipase types. It is obvious to finalize the eROP at low reaction times and conversions in order to obtain lower side reactions and comparable HEMA addition. Furthermore, the lower enzyme amount might be preferable in order to realise higher HEMA addition, lower methacrylate transfer, comparable total methacrylate end-groups, and minimum EG inside the chains. HEMA/CL ratio can also be chosen minimum as both of the side reactions seemed to be lower at both temperatures and enzyme amounts, still conserving the total methacrylate amount sufficient. In addition to these, higher molecular weight and polymerization yield of macromonomers can be obtained at lower initiator/lactone ratios. To synthesize α,ω-methacrylated macromonomer for the application as a crosslinking agent in UV polymerization, it was benefited from the previously investigated side-reactions during eROP of CL when an ester containing initiator presented in the reactor. The double methacrylation of the PCL chains was evaluated to be a successful route, since the one-pot synthesis comprised of the primary synthesis of PCL enzymatically, and subsequent tailoring of the methacrylate groups onto the chains provided that all the water molecules were removed from the reaction mixture with high vacuum for high a conversion time. Furthermore, the conversion values without the usage of either PEGMA-950 or DMPCL didn't give high conversion values of DMPCL and PEGMA-950. Therefore, the concurrent usage of DMPCL and PEGMA-950 in photopolymerization provided a synergetic influence for the conversion of both macromonomers with the help of TMPTA. The feed mole ratios 0.25, 0.50 and 0.75 for DMPCL (DMPCL/Total macromonomers) inside the photopolymerization mixture all gave high polymerization yields. Consequently, enzymatically polymerized dimethacrylated PCL macromonomer with average molecular weight of 4400 g/mole and 0.84 ratio of the total methacrylate end-groups was found to be an efficient crosslinking agent in photopolymerization and obtaining amphiphilic networks. It was noteworthy that the low Tg and Tm values of the amphiphilic networks revealed the rubbery and elastic behaviour of the materials. The enzymatic synthesis of PCL-based macrophotoinitiator was performed successfully. The macrophotoinitiator successfully photopolymerized the acrylate monomers: butyl acrylate, benzyl acrylate, tetrahydrofurfuryl acrylate, 2,2,2-trifluoroethyl acrylate, 2-hydroxyethyl acrylate and poly (ethylene glycol) methyl ether acrylate ~ 480 g/mole). Benzyl acrylate and tetrahydrofurfuryl acrylate had the highest conversion values. The block copolymer structure of poly(CL-b-BzA) and high conversion was confirmed with a single and broad Tg value with a high step decrease of the specific heat capacity. The relatively high dry polymer conversions for gel formation by using HEA and PEGMEA-480 monomers in photopolymerization also proved the efficiency of amphiphilic polymer synthesis via PCL based macrophotoinitiator. The low Tg value, thus the rubbery state, of the amphiphilic gels also made it possible for their usage in biomedical applications together with the biocompatible nature of the employed macromonomers. A chemoenzymatic route was utilized in order to synthesize amphiphilic diblock copolymer (P(CL)n-b¬-P(PEGMEA)m) and an amphiphilic triblock copolymer comprising zwitterionic monomer units (P(CL)n-b¬-P(PEGMEA)m-b-P(SMBA)k). It should be noted that the third polymer segment was installed by the synthesis of a methacrylate via ATRP onto an polyacrylate based diblock macroinitiator. Furthermore, the low solubility of the diblock copolymer in the reaction solvent ethanol/water mixture was also one of the challenging points of the third monomer addition. Another barrier for both PEGMEA-480 and SBMA ATRP polymerizations might be the steric hinderence of PEGMEA-480 brush segments together with the possible entaglements of the PEG chains. However, PEGMEA-480 conversion was calculated as 65% and SBMA was proven to be polymerized with diblock ATRP macroinitiator. Amphiphilic diblock copolymers comprised of PCL and PEG synthesized via photopolymerization and ATRP approaches both had antibacterial activity against S. aureus (Gram positive) and E. coli (Gram negative). The triblock copolymer, based on PCL, PEG and PSMBA was only antibacterial against S. aureus. However, neither of the polymers provided antifungal activity against A. niger. Antifouling feature assay might also be performed for the synthesized polymers, since composing antifouling surfaces is one of the candidate routes to obtain antibacterial activity due to their capability of inhibition of the protein based molecules which are employed by microorganisms to simplify their settlemt on surfaces. Protein adsorption test might be a method to investigate antifouling features. Consequently, enzymatic ring-opening polymerization in combination with photopolymerization or ATRP was found to be an approach to synthesize polymers performing antibacterial properties which might find applications in biomedical and marine uses.
Synthesis of some functional conducting polymers, characterization, Mott-Schottky analysis and sensor applications
Until the late 1970's, polymeric materials were associated with low conductivity. In fact, this low conductivity has been used to advantage in applying polymeric materials as insulators. This concept has changed with discovery of conducting polyacetylene and declaration of poly-p-phenylene, polypyrrole, polythiophene, polyaniline, polycarbazole, and polyindole among other polymers. These polymers are called as conducting polymers (CPs). CPs, thus, have attracted strong interest in materials science because they are utilized for advanced technologies due to their interesting and unique electrical conductivity and electroactivity. They are mostly used in promissing technological applications such as biosensor, biomedical science, electrochromic, photovoltaic devices, batteries, light-emitting diodes, supercapacitors, and actuators. Electrochemical impedance spectroscopy (EIS) is the most widely used one of electroanalytical techniques. EIS is a non destructive methode and useful in research of electrode / electrolyte interface providing sensitive information about the surface. The biggest advantage of this technique is that it provides the distinction in the different processes which are simultaneously taken place on the surface of electrode. Several electronic characteristics of a semicocnducting film can be obtained from the semiconductor/liquid interface behavior when a bias voltage is applied to modulate the width of the space-charge capacitance, and thus the value of the capacitance.The most common and established method for the capacitance determination is impedance spectroscopy technique. Mott-Schottky analysis can be performed by using EIS technique to obtain semicocnducting parameter of semiconducting film where capacitance voltage measurement is carried out, and thus the carrier density, the flat-band potential of semiconductor materials can be easly found. Important process can take place in the semicoductor modifed electrode when immersed in electrolyte such as ions adsorption, double layer, charge transfer between the electrode and electrolyte, during this process, a charge separation will occur because of electron transfer across the interface. and mass transfer. The study of interface of semiconductor/electrolyte is important issue due to both basic and practical aspect of science. Conducting polymers as the electrode material have been mostly used the aferomentioned potential applications. It has been observed that the interphase properties of the electrode and the electrolyte affect processability of these materials. The electrical conductivity of organic semiconductors depends on the carrier density (electron or hole) and carrier mobility. Carrier density is affected by the some factors which are morphology of the solid film, the nature of the organic semiconductors and electroylte. Polypyrrole is a widely used conducting polymer in terms of electrical conductivity and environmental stability. Pyrrole-1-propionic acid (PPA), pyrrole derivative, has emerged as a novel material with biosensor construction and reported in a few papers. Poly(pyrrole-1-propionic acid) (Poly(PPA)) film in biosensor construction enables rapid diffusion, fast response and high response signal due to its low conductivity and self-limiting growth. Huge amount of research dedicated to the electropolymerization of pyrrole and its derivatives in the last two decades. However, substituted pyrrole on the 3-position have received much less attention compared to corresponding thiophenes due to the limited availability of 3-substituted pyrroles, their chemical synthesis being quite complex. On the other hand, substitution in the 3-position of the pyrrole ring gives the possibility of introducing specific functional groups on the polypyrrole chain. Pyrrole-3-carboxylic acid (PCA) is 3-substituted pyrrole derivative which can be polymerized the 2-5 position offers the possibility of attaching biomaterial. Electrochemically synthesized poly(pyrrole-3-carboxylic acid) (PPCA) were used in ion exchange, pH measurements, and sensor. Polycarbazole (PCz) and its derivatives have been widely studied in the literature. PCz is a high thermal stability, mechanical strength conducting polymer causing the diffuclty in workability. However, PCz has drew interest with developments in synthetic methodology. Electroactive PCz has found applications in electrochromic devices, transistors, in electrochemical sensors. Carbazole-9-acetic acid (CzA) is important derivative of carbazole because carboxylic acid group is of the active functional group, and it plays an important role in further modificiation. In the first part of thesis, PPA was electrochemically polymerized on a glassy carbon electrode (GCE) in various electrolytes (NaClO4, Et4NBF4, Bu4NClO4,and Bu4NPF6) using cyclic voltammetry (CV). The structure and morphology of the modified electrode was characterized by fourier transform infrared spectroscopy-attenuated total reflectance (FTIR-ATR), scanning electron microscopy (SEM), and atomic force microscopy (AFM). The morphological characterizations of the poly(PPA) films synthesized in the various supporting electrolyte solutions were demonstrated by SEM and AFM. Electrochemical impedance spectroscopy (EIS) and Mott–Schottky (M–S) analysis were performed to collect information about the semiconducting properties of the poly(PPA) films. From the Mott–Schottky analysis, the carrier densities (ND) of the poly(PPA) films obtained were 3.25×1016,1.59×1016, 1.17×1016, and 0.52×1016 cm-3,and the flat-band potentials (EFB) were 0.41, 0.32, 0.37, and 0.36 V for the poly(PPA) films in NaClO4, Et4NBF4, Bu4NClO4, Bu4NPF6 , respectively. The resulting Mott–Schottky plots of the poly(PPA) films indicate that the films are p-type semiconductors. EIS analysis were performed to determine the capacitive behaviors by variation of electrolyte types in a monomer-free solution. An equivalent-circuit model of R(W(CR)(QR))(CR) was used to fit the theoretical and experimental data to interpret the polymer electrode/electrolyte interface properties and to provide information about equivalent circuit parameters with variation of electroltye nature. In the second part of thesis, we describes that the fabrication of Indium Tin Oxide /gold nanoparticles/nickel oxide/poly(Pyrrole-N-propionic acid) (ITO/GNPs/NiO/poly(PPA)) multilayered film, and modification with Tyrosinase (Ty).The ITO/GNPs/NiO/poly(PPA) electrode was fabricated by sequential electrochemical assembly onto ITO substrate which electrochemical deposition provides a facile, inexpensive technique for synthesis of multilayered film within the adherent morphology with controllable film thickness. CV, FTIR-ATR, SEM, and AFM were used to characterize the film assembly processes. The properties of a semiconductor/electrolyte interface were investigated based on the Mott–Schottky approach for the modified electrodes, with the flat band potential according to the potential intercept and the carrier density according to the linear slopes. The ND and EFB of ITO/GNPs/NiO/poly(PPA) were obtained as 2.48x1021 cm-3 and 0.26 V, respectively. Tyrosinase was immobilized using carbodiimide coupling reaction. The bioelectrode was characterized by FTIR-ATR, SEM, AFM, electrochemical impedance spectroscopy (EIS). A Randles equivalent circuit was introduced for modeling the performance of impedimetric biosensing for the detection of the dopamine (DP) and the interface of bioelectrode/electrolyte. The EIS of the ITO/GNPs/NiO/poly(PPA)-Ty exhibited significant changes in the charge transfer resistance (RCT) value toward the detection of dopamine over a linear range of 80 µM to 0.2 mM with a limit of detection (LOD) of 5.46 µM. In the third part of thesis, pyrrole-3-carboxylic acid (PCA) was electropolymerized on a GCE. The Electropolymerization process was performed in 0.1 M NaClO4/ACN, Et4NBF4/ACN using cyclic voltammetry. Urease (Urs) was immobilized onto poly(pyrrole-3-carboxylic acid) (PPCA) modified GCE via covalent binding, exploiting EDC/NHS chemistry. Electrochemical impedance spectroscopy was used to investigate the interfacial behavior of urease immobilized PPCA surfaces at open circuit potential (OCP). The impedance spectra were fitted before and after immobilization of Urs using equivalent circuits of R(C(R(Q(RW)))), which describe changes due to the Urs immobilization process. After immobilization of urease onto the PPCA matrix, the RCT increased for electrodes, which RCT of urease immobilized PPCA-NaClO4 matrixes were lower than that of the urease immobilized PPCA-Et4NBF4 matrixes indicating higher charge transfer ability. A decrease in double layer capacitance (Cdl) values when Urs was immobilized at the PPCA-NaClO4 electrode surface was observed, whereas an increase in Cdl values at the PPCA-Et4NBF4 electrode surface was observed. The Mott-Schottky approach was performed to investigate interface properties of the protein modified polymer matrix. It was possible to observe that the processes occurred by the immobilization of enzyme on the polymer matrix with changes in the semiconducting properties of the PPCA films. The electrodes with immobilization of urease resulted in a n-type semiconducting behavior revealing a positive slope. An increase in acceptor concentration of the electrodes, and a shift of the EFB to more positive values with increasing amount of urease was observed as well. The Urs based electrode (PPCA-NaClO4-Urs) was used for detection of urea, which was detected in range of 0.9 to 14 mM with a detection limit (LOD) of 8.28 µM. In the fourth part of thesis, the electrochemical polymerization of 9-carbazole acetic acid (CzA) monomer was performed in various feed ratios of room-temperature ionic liquid (RTIL), 1-butyl-3-methylimidazolium tetrafluoroborate (BMIMBF4) in acetonitrile (ACN) to investigate the effect of RTIL on morphology, impedance, capacitance, and semiconducting properties. It was observed that the low amounts of the RTIL (10 and 20 %) in the mixture improve the electrochemical polymerization process compared to the RTIL-free electrolyte. Indeed, after a certain amount % BMIMBF4 which was threshold (40%), the process turned strongly unfavored. SEM was used to understand the influence of the feed ratio of BMIMBF4 to ACN on the surface structure of obtained polymer films. The surface morphology of poly(9-carbazole acetic acid) (PCzA) revealed dependence on the feed ratio of BMIMBF4. Electrochemical impedance spectroscopic experiments were performed in a pure BMIMBF4 (100 %) indicated that as the feed ratio of BMIMBF4 increased, the capacitive behavior of the polymer decreased. From the Mott–Schottky analysis, the highest flat band potential (EFB=2.87 V) was obtained for the 40% PCzA-BMIMBF4 film.
Synthesis of amphiphilic graft copolymer via click chemistry
The proton exchange membrane fuel cell (PEMFC) that is also known as polymer electrolyte membrane fuel cell uses a acidic and water-base polymer membrane as electrolyte with Pt electrodes. Operating temperatures of PEMFCs are below 100 oC and it can be adapted electrical output with dynamic power demands. These cells must be worked with pure hydrogen since it needs relatively low temperatures and costly metal based electrodes. Nowadays, PEMFCs are used in industry in widening scale, but mostly used in light duty vehicles, material handling vehicles, etc. The issues like chemical degradation at elevated temperatures, poor ionic conductivities at low water content and high cost, restrict the commercial proton exchange membranes. Therefore, alternative membrane researches for fuel cells maintain timeliness. During the last decades, chemical resistance, weathering elements and oxidants, low surface energy properties and hydrophobic properties make the fluoropolymers interesting for fuel cell membranes. Especially amphiphilic fluorinated graft copolymers have a great importance for PEMFC applications. P(VDF-co-CTFE) is one of the fluoropolymer that can be used in this applications due to its excellent properties such as chemical resistance and conductivity. As a result of this, a lot of reasearch have been reported to obtain alternative fuel cell membranes. Atom transfer radical polymerization (ATRP) is a controlled free radical polymerization technique. Well-defined amphiphilic graft copolymers with controlled molecular weight, well-dispersed macromolecules, terminal functionalities and chain architectures can be achieved in a polymer via this method. Also, ATRP permits to synthesize advanceed fluorinated polymers. Click chemistry is one of the methods to unite molecules quickly. High yielded, stereospecific, modular products can be obtained easily with this method. Recently, there are several progress have been identified such as copper(I)-catalyzed azide alkyne reaction and this technique have huge concern for polymer chemist. In this study, P(VDF-co-CTFE) was selected for the main chain and tried to synthesize a suitable molecule for PEMFC. Firstly, some ionic molecules are tried such as 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS), 2-acrylamido-2-methyl-1-propanesulfonic acid triethylamine salt (AMPS-TEA) and 3-sulfopropyl methacrylate potassium salt (SPMAK) to obtain grafted fluorinated copolymers, but covalent bonding did not observed. So, methyl methacrylate (MMA) and tert-butyl acrylate (tBA) are used to understand the reactivity of P(VDF-co-CTFE) on hand. As a result of these studies, PtBA was selected as pendant group. Then the PtBA was grafted from azidated P(VDF-co-CTFE) with click chemistry method. The resulted polymers were characterized with FT-IR, 1H-NMR, DSC and GPC instruments. Also, electrochemical impedance measurements and contact angle analysis were investigated.
Reaction of acetophenone-formaldehyde resin with s-triazone compounds for fire resistance polyurethane
These days; the use of flame retardants is significantly increasing, especially since plastics are an important part of our daily lives. These materials in general; Bromine, chlorine, metal hydroxide, nitrogen-based, phosphorous-containing or mixtures. The annual consumption of flame retardants is more than 1.5 million in the world market. It costs about $ 2.4 billion. It is seen that the market of flame retardants has increased by 5% per year. The flame retardants could be inorganic or organic. These chemicals can sometimes be used alone as an additive, sometimes in the form of a binary formulation. The important problem here is that these flame retardants must be well dispersed in the polymer matrix. Currently, bromine-based flame retardants are used and their using is limited because side effects are observed. The use of chlorine- and bromine-based flame retardant materials has been restricted or prohibited periodically after 2000 due to the generation of harmful gases and harmful gases to the environment. This has prompted the chemical industry to seek a new generation of flame retardant materials whose distribution is good in polymer, and which is unlikely to produce toxic waste after combustion. The discovery of polyurethane dates back to the year 1937 by Otto Bayer and his coworkers at the laboratories of I.G. Farben in Leverkusen, Germany. The initial works focussed on PU products obtained from aliphatic diisocyanate and diamine forming polyurea, till the interesting properties of PU obtained from an aliphatic diisocyanate and glycol, were realized. Polyisocyanates became commercially available in the year 1952, soon after the commercial scale production of PU was witnessed (after World War II) from toluene diisocyanate (TDI) and polyester polyols. In the years that followed (1952-1954), different polyester-polyisocyanate systems were developed by Bayer. Polyester polyols were gradually replaced by polyether polyols owing to their several advantages such as low cost, ease of handling, and improved hydrolytic stability over the former. Poly(tetramethylene ether) glycol (PTMG), was introduced by DuPont in 1956 by polymerizing tetrahydrofuran, as the first commercially available polyether polyol. Later, in 1957, BASF and Dow Chemical produced polyalkylene glycols. Based on PTMG and 4,4'- diphenylmethane diisocyanate (MDI), and ethylene diamine, a Spandex fibre called Lycra was produced by Dupont. With the decades, PU graduated from flexible PU foams (1960) to rigid PU foams (polyisocyanurate foams-1967) as several blowing agents, polyether polyols, and polymeric isocyanate such as poly methylene diphenyl diisocyanate (PMDI) became available. These PMDI based PU foams showed good thermal resistance and flame retardance. Isocyanates are essential components required for PU synthesis. These are di-or polyfunctional isocyanates containg two or more than two –NCO groups per molecule. These can be aliphatic, cycloaliphatic, polycyclic or aromatic in nature such as TDI, MDI, xylene diisocyanate (XDI), meta-tetramethylxylylene diisocyanate (TMXDI), hydrogenated xylene diisocyanate (HXDI), naphthalene 1,5- diisocyanate (NDI), pphenylene diisocyanate (PPDI), 3,3'-dimethyldiphenyl-4, 4'- diisocyanate (DDDI), 1,6 hexamethylene diisocyanate (HDI), 2,2,4- trimethylhexamethylene diisocyanate (TMDI), isophorone diisocyanate (IPDI), 4,4'- dicyclohexylmethane diisocyanate (H12MDI), norbornane diisocyanate (NDI), 4,4'- dibenzyl diisocyanate (DBDI). Figure 1 shows examples of some common isocyanates. Substances bearing plurality of hydroxyl groups are termed as spolyols. They may also contain ester, ether, amide, acrylic, metal, metalloid and other functionalities, along with hydroxyl groups. Polyester polyols (PEP) consist of ester and hydroxylic groups in one backbone. They are generally prepared by the condensation reaction between glycols, i.e., ethylene glycol, 1,4-butane diol, 1,6-hexane diol and a dicarboxylic acid/anhydride (aliphatic or aromatic). The properties of PU also depend upon the degree of cross-linking as well as molecular weight of the starting PEP. While highly branched PEP result in rigid PU with good heat and chemical resistance, less branched PEP give PU with good flexibility (at low temperature) and low chemical resistance. Similarly, low molecular weight polyols produce rigid PU while high molecular weight long chain polyols yield flexible PU. An excellent example of naturally occurring PEP is Castor oil. Other vegetable oils (VO) by chemical transformations also result in PEP. PEP are susceptible to hydrolysis due to the presence of ester groups, and this also leads to the deterioration of their mechanical properties. This problem can be overcome by the addition of little amount of carbodiimides. In general, reactive flame retardants are composed of halogens and phosphorous. Phosphorus-containing flame retardants may be incorporated into the polymer matrix as an inorganic additive or covalently bonded to the polymer main chain to impart flame retardant properties to the material. In the solid phase, the phosphoruscontaining flame retardant reacts with oxygen in the polymer chain or matrix during heating or combustion. Phosphorus compounds which interact with the polymer form phosphoric acid, and the dimerization of these molecules results in the removal of the water molecules and pyrophosphate formation. Phosphorus based additives as well as phosphorus structures covalently bonded to the polymer chain are both academic and industrial interest. The incorporation of additives into the polymer matrix covalently, or the incorporation and use of monomers in flame retardant structures and polymerisation, is at the forefront of new strategies for "nonflammable polymers." There are hundreds of different flame retardants. They are often broken into categories based on chemical structure and properties. In general, flame retardants are grouped based on whether they contain bromine, chlorine, phosphorus, nitrogen, metals, or boron. Brominated flame retardants — Contain bromine and are the most abundantly used flame retardants. Used in many consumer goods, including electronics, furniture, building materials, etc. and have been linked to endocrine disruption among other effects. Polybrominated diphenyl ethers (PBDE's) PBDEs do not chemically bind with the products to which they are added (furniture, electronics, etc.) so they easily release from these products and enter air and dust. PBDEs can lower birth weight/length of children, and impair neurological development. Tetrabromobisphenol A (TBBPA) Widely used to make computer circuit boards and electronics. Also used in some textiles and paper, or as an additive in other flame retardants. Hexabromocyclododecane (HBCD) An additive primarily used in polystyrene foam building materials. The primary risk to humans is from leaching out of products and getting into indoor dust. Low levels of HBCD have also been found in some food products. Organophosphate flame retardants (OPFRs) With the phasing out of PBDEs, some OPFRs have been identified as replacements. NIEHS-supported researchers are also looking at the health effects of newer flame retardant alternatives that are being brought to market. In this study, condensation product of acetophenone formaldehyde resin (AFR) with alendronic acid s-triazone was produced and modified resins were added 20% , 30% of polyol to the solution at room temperature, used as polyol in the production of rigid polyurethane form in order to improve its fire resistance. AFR was synthesized primarily in basic medium. Then, AFR was modified via their hydroxyl groups by reaction with dimethylol s-triazone that was produced by the reaction of urea with the mixture of formaldehyde and alendronic acid. S-triazone reacts with formaldehyde in the presence of basic catalyst to give dimethylol derivatives. Methylol derivatives of s-triazone give condensation products in an acid media with resin. The mol ratio of s-triazone / resin was about 1/5. Insertion of functional striazone cyclic structure to the AF-Resin effected its physical properties considerably. The products were characterized by FTIR, 1H-NMR, 13C-NMR , 31PNMR, TGA and UL94 analysis. In the combustion tests the foam made from the modified resins self-extinguishes after a certain period of time, while the polyurethane foam obtained from the unmodified resin on the left side continues to burn until completely carbonized. Also, the foams obtained from the modified resins have a rigid structure. Cyclohexanone - formaldehyde resins can be produced in acid and basic media successfully. However, acetophenone – formaldehyde resin can only be produced in basic media in presence of potassium hydroxide. Acetophenone – formaldehyde resin formed in acidic media with very low yield and its softening point was about 20- 250C. The results obtained according to the study are as follows; Acetophenone - formaldehyde resin can be obtained efficiently in the presence of potassium hydroxide in basic medium. Resins can be modified with s-triazone compounds. The materials used in the modification of the resins are readily available and inexpensive materials such as urea and formaldehyde. Depending on the composition of the resin, modification of the resin may change some physical properties such as solubility and flammability. It has been observed that the modified resins have a positive effect on the polyurethane nonflammability such as foam. These results may contribute to the use of resin in the area of incombustibility.
PI-PI stacking of polyesters containing pyrene in main chain to the multi-walled carbon nanotube surface
Various types of polyesters having electron deficient alkyne units in the main chain were synthesized by using acetylene dicarboxylic acid and different diols. Then, 1,3-dipolar cycloaddition reactions were performed between these polyesters and an ester molecule having aromatic pyrene moiety to form triazole ring in the structure. These polyesters having pyrene functioanlity in the structure were interacted with carbon nanotubes in different types of solvent to obtain song pi-pi intearctions between nanotubes and polymer chains and various characterization methods were applied.
Computational and experimental approaches to develop minocycline imprinted hydrogels and determination of their drug release performance
The main purpose of this thesis is to produce new formulations for contact lens synthesis which have a wide user group nowadays and that are used in the correction of visual defects and to develop suitable hydrogels for contact lenses that are featured of drug release in the treatment of chronic eye diseases such as eye pressure, xerophthalmia, and corneal neovascularization. Contact lenses are most commonly known as optical instruments that are used for cosmetic or therapeutic purposes to eliminate visual disorders. Contact lenses in today's world are made of hydrogel materials, and their soft structure provides ease of use. Biocompatibility of hydrogels with other biomaterials are higher because of their high-water content and chemical properties. Besides the contact lenses; controlled drug delivery systems, wound dressings, regenerative tissue scaffolds, organ linings, membranes with biosensor, microfluidic valves, and absorbents are set a good example for other hydrogel applications. In this study, hydrogel syntheses with high biocompatibility that can be used in contact lens applications are performed. According to the recent studies, newly developed contact lenses are planned to use in the treatment of various diseases. In this study, drug release characteristics of drug loaded hydrogel by using absorption and imprinting methods were investigated. In this study, molecular imprinting method was used to produce hydrogels with controlled drug delivery characteristics. In this study, the minocycline molecule was selected as the target molecule to be imprinted. A computerized calculation method was used in order to select suitable monomers for the synthesis of hydrogels carrying drug-delivery characteristic. By the help of molecular simulation method, the interactions of expensive and rare monomers and drug molecules are calculated, then appropriate monomer is selected. Molecular dynamic (MD) method was used in the molecular simulation stage. Functional monomers that may be selected for use in the synthesis of hydrogels include acrylic acid (AA), methacrylic acid, itaconic acid, 1 N ethyl acryl amide, 1 N isopropyl acryl amide, and hydroxymethyl acryl amide. MD calculations were done with the Materials Studio 5 Forcite module. The total simulation period is 5 nanoseconds. As a result of MD studies, it is clearly seen that itaconic acid and hydroxyethyl acrylamide monomers have the best interactivity with the minocycline molecule. The effect on the interaction between the monomer-mold molecule on the prepolymerization step of the cross-linking ratio was investigated by MD studies. In this stage of the study, experimentally applied monomer ratios were inserted into the simulation box and the cross linker - minocycline and functional monomer - interactions were investigated and compared with the experimental results. MD simulations have been conducted in the previously specified conditions. In the experimental part of the study, minocycline-printed and non-imprinted hydrogels were synthesized and then the effect of cross-linking ratio on the molecular imprinting method was investigated. Hydroxyethyl methacrylate (HEMA) was used as the main chain in the hydrogel synthesis, acrylic acid (AA) was used as the functional monomer, and ethylene glycol dimethacrylate (EGDMA) was used as the cross-linking agent. 2,2'-azobis (2,4-dimethyl-pentanenitrile) (Vazo52) was selected as the thermal initiator. It is imprinted to the minocycline polymer matrix as the mold molecule. Structural characterization of the synthesized hydrogels was conducted by Fourier transformed infrared (FT-IR) spectroscopy. According to FT-IR results, hydrogel synthesis was completed successfully. The swelling behaviors of imprinted and non-imprinted hydrogels were carried out at their loading and release temperatures of 4 °C and 37 °C. When the swelling behavior of hydrogels is investigated, it is clearly seen that temperature has no effect. Differential scanning calorimetry (DSC) was used for the thermal characterization of the synthesized hydrogels. Controlled drug delivery behavior of synthesized and characterized hydrogels are investigated. The drug loading capacities of the synthesized hydrogels were measured at 4 °C and the drug release performance was tested at 37 °C in 0.9% NaCl solution (saline solution) in order to apply the body image. The mechanism behind these findings was investigated by MD studies. Accordingly, in systems containing 2% and 3% EGDMA, the frequency and intensity of the interaction between AA acid and drug is higher than 1% EGDMA studies. According to the obtained loading and release data, hydrogel molecular imprinting properties with the ratio of 2% and 3% EGDMA are shown. In this ratio, the imprinting factor (IF) of the hydrogel that contains the EGDMA is greater than 1 and the drug release performance is higher than the non-imprinted hydrogel which contains 2% and 3% EGDMA.
Development of molecularly imprinted hydrogels for drug release systems
In the past few decades, hydrogels have been a focal point of many researches in the biomedical and pharmaceutical fields. They offer great promise for applications in cell therapy, tissue engineering and as vehicles for controlled drug release. Recent studies in the area of molecularly imprinted hydrogels in controlled release of drugs highlighted these materials as a promising platform for controlled ocular drug delivery systems. The purpose of this study was to fabricate novel Doxycycline Hyclate (DOX)-imprinted ocular controlled release hydrogels by establishing a relationship between material structure and its performances . The material-property relationship was established and used to predict the releasing performances of the DOX-imprinted hydrogels. Initially, a systematic method was designed to investigate the parameters affecting the fabrication of MIPs by thermal and UV induced polymerization. Effectively optimization of the polymerization conditions including reaction type, initiator concentration, reaction period and reaction temperature resulted in high degree of monomer conversion. Design of experiments (DOE) as a systematic approach to engineering problem-solving was applied using MINITAB to ensure the generation of valid and defensible conclusions from the model parameters. The model parameters used in the pre-polymerization were comprised of crosslinker type, crosslinker ratio, monomer type, monomer ratio and drug ratio. Pre-polymerization interactions between template (DOX) and model parameters were investigated via UV measurements and binding studies. In the dissertation, statistical methods were also adopted to releasing pattern of DOX-imprinted hydrogels. Statistical analysis was performed with ANOVA (Analysis of Variance) with the data obtained from the drug release results. Four different releasing criterias were used to obtain regression models separately. The advantage of regression model lies in its flexibility regarding decision making process in controlled release hydrogel formulation prior to experimentation. Running the models obtained from statistical analysis played a key role in reduction of time and number of experiments. Furthermore, the obtained models facilitated optimization of the desired properties of the formulations for the subsequent synthesized materials. Response optimizer was used to decide the optimum formulation based on the desired properties. Based on the predicted optimum formulations new hydrogels were synthesized and the obtained results were compared with the predicted ones. The results showed that the predictive formulations obtained with the experimental design were consistent with the experimental results. Both imprinted and non-imprinted hydrogels were characterized by Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC). Morphological differences between non-imprinted and imprinted hydrogels were clarified by Scanning electron microscope (SEM) analysis. Structural analysis were conducted by NMR analysis. The effects of modelling parameters on release and loading performances of both imprinted and non-imprinted hydrogels were investigated experimentally. In this stage, interactions between the variables were explained via non-covalent chemistry. Then, based on the release performances, drug release kinetic profiles were evaluated. The structural and mass transfer properties of molecularly imprinted and non-imprinted hydrogels were explored for controlled drug delivery applications. Swelling behaviors of all hydrogel systems were studied in loading solution, releasing medium and distilled water. Then, the swelling behavior of the hydrogel systems were used to determine their structural properties. The determination was based on the calculation of volume fraction in swollen state (V2,s), the mesh size (ξ), and the average molecular weight between crosslinks (M̅c ) of the hydrogels. Thereafter, to obtain a more careful design of DOX-imprinted hydrogels along with network design, mathematical approaches were used to determine drug transport mechanisms of all hydrogels. The Mathematical models were used to fit the release data in order to gain insight into the release mechanism. For this purpose, Korsmeyer-Peppas and Higuchi Equations was used to understand the transport mechanism of drug molecules. Korsmeyer Peppas with the largest regression coefficient was determined as the best-fit model. The non-imprinted hydrogels had higher Korsmeyer release exponent (n) , indicating generally super case II transport. The DOX-imprinted hydrogels had relatively low n values and therefore, exhibited non-Fickian transport mechanism, in general. According to loading and release performances, DOX-imprinted hydrogel samples which included IA and TEGDMA, displayed great controlled drug release performance compared to the other hydrogels. According to this results, the hydrogels were synthesized in both high and low crosslinker ratios with IA-TEGDMA and their performances were compared with the non-imprinted counterparts. DOX-imprinted hydrogels with high crosslinker ratios provided highly effective controlled release performance than the others. This thesis study showed that experimental studies successfully used with statistical modelling methods. At the same time, the parameters affecting the properties of the imprinted hydrogels have been successfully defined and their interactions with each other has been examined. The results of the study showed that each imprinting system exhibited different characteristics due to diffirent affinities towards template molecule. Experimental and statistical studies could be used in a meaningful way and these studies contained informative information for studies with a low crosslinker ratio in the absence of solvent during polymerization. Finally, the thesis study will be followed by a mutli-disciplinary approach by biologists, physicians, chemical engineers and chemists in order to develop contact lens and perform in vivo studies for the treatment of neovascularization via TUBITAK supports (Project No:114M459).
Synthesis and characterization of one-side polypyrrole coated conductive and flexible polyurethane films
Recently, conductive polymers have been the focus for scientists cause of wide application areas such as bio and chemical sensors, antistatic coatings, tissue engineering, rechargeable batteries, corrosion-inhibiting films and so on. Polypyrrole (PPy) is one of the most important conductive polymer cause of its advantages like, good electrical conductivity by its conjugated structure, relative ease to synthesis and oxidative stability compared with other conductive polymers. PPy can be synthesized by electrochemical or chemical oxidation polymerization of pyrrole (Py) in different kind of organic solvents and in aqueous media. On the other hand, polyurethane (PU) is one of the most multipurpose and useful engineering insulator polymer cause of its good mechanical properties. It is synthesized with using a prepolymer isocyanate, a polyol and a catalyst. That reactants have many different types to give to final PU product varied physical and chemical properties. In last decades, to improve individual materials' mechanical properties, to achieve products with high properties like resistance to environment, chemicals or flame or to obtain them in light weight with low costs, composite materials have been studied. There are also composite studies about PU and PPy combination. In this study, one-side PPy coated conductive and flexible PU/PPy composite films were synthesized in the acetonitrile (ACN)/H2O interface as a new alternative to two side coated PU films which have already reported in literature. Composite films were prepared by chemical oxidative polymerization method. First, PU flexible films were synthesized by the reaction of triol with the excess of isocyanate based prepolymer by using a catalyst and resulting PU has free reactive -NCO groups. Then, PPy was coated onto PU film by the reaction of aqueous solution of Py contacted to one side of the film, with cerium ammonium nitrate (CAN) in ACN contacted to the other side. Since, PU film had softened with ACN, the diffusion of Py into PU matrix become easier and PPy formation occured on the only ACN side of the film (PU/PPy). This PU/PPy composites were characterized by four-probe electrical conductivity, Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Scanning Electron Microscope (SEM) measurements. Mechanical properties of the composite films were obtained by Zwick Roell tensile tester. The thickness of PPy coating was determined as 0.015 μm by using polarized microscope imagines of cross section of composite. The glass transition temperature (Tg) was obtained as -60.38 °C and the highest conductivity of PPy side of PU/PPy composites was obtained as 3.5x10-4 S.cm-1, while the water side of PU film was still insulator.
Synthesis of tris(hydroxymethyl)aminomethane modified polystyrene based polymeric sorbent and removal of boron from aqueous solutions
Boron is placed in-group 13 of periodic table and found at low concentration in a wide area range such as rock, soil and water in nature. Boron is used in many industrial applications, especially in insulation, retardant fiberglass and ceramic industry. In addition, boron is an essential element for living organism systems. Excess amount of it causes water and other environmental pollution. As high concentration causes adverse effects, boron level is limited in irrigation or drinking water. The World Health Organization (WHO) currently recommends the concentration of boron in drinking water to be 2.4 mg/L. Consequently, boron removal from wastewater is an important topic. Various removal methods are available for boron separation. Some of them are; precipitation-coagulation, solvent extraction, membrane filtration, reverse osmosis, electro dialysis and adsorption. Adsorption is completely different from others because it is a very useful method and needs low price equipment for removal of boron from wastewater. In the first part of this study, tris(hydroxymethyl)aminomethane was interacted with poly(vinyl benzyl chloride) resin to obtain boron selective sorbent. The resin was characterized with FT-IR spectroscopy to determine the functional groups important for boron sensitivity. Total amine content of the resin was calculated analytically as 2.45 mmol.g-1 sorbent. In the second part of the study, experimental measurements were performed on modified resin about boron adsorption. Adsorption capacity of the sorbent was investigated for different boron concentrations. Boron loading capacity of the sorbent is 2.17 mmol.g-1 resin, in non-buffered conditions. Sorption behavior was also observed in the presence of different concentration foreign ions such as Ca+2 and Mg+2. Besides that, boron adsorption was further studied at varying pH in the range of 2.0-10.0. Kinetics of boron sorption was performed at low concentration to investigate the efficiency of the modified resin at this condition. For this purpose, pseudo-first order, pseudo-second order and intraparticular diffusion kinetics models were used. Regeneration of the loaded resin was also studied. 2.10 mmol.g-1 boric acid was recovered of the loaded sample, which showed that the resin was able to desorp nearly completely.
Synthesis of low noise, fast drying packaging tape adhesive via emulsion polymerization
Adhesives are defined as materials used to bond other materials, mainly on their surfaces through adhesion and cohesion. Pressure sensitive adhesives (PSAs) are ensure instantaneous adhesion by application of a light pressure and can be organic solvent- or water-based (dispersions), or in a solvent-free form as in the case of hot melt . Water-borne adhesives comprise acrylics, natural and synthetic rubber latexes, and ethylene vinyl acetate dispersions. As known, the interest in aqueous acrylic dispersions PSA grew with the need to solve solvent emission problems. The most common applications for water based pressure sensitive adhesives are tapes and labels. The packaging tape market is a growing worldwide industrial market. Developments in dispersion polymer chemistry have largely converted this market in a safe water based polymer dispersion user. Improvements on the application machine techniques have led to significant productivity gains. Although there are a few dispersion adhesives in the marketplace, still improvements are needed in the polymer side to reduce undesired noise levels when unwinding the tapes at the packaging line as well as increase drying fastness for the coating on higher speed machines. The importance of viscosity control at high shear rates is a very well known phenomena and the particle size is the key for the control on rheology. Small particles are less affected at high shear rates which increase the importance of polymodal or broad particle size distribution. Although both solvent- and water-borne acrylic PSAs are derived from the same monomers, the adhesive and cohesive properties of emulsion PSAs are different. A likely explanation for this inferiority is given as the more heterogeneous morphology of waterborne materials. As mentioned in several resources, PSA must be soft and tacky. Thus, its glass transition temperature (Tg) should be low, ranging from -20 ◦C to -60 ◦C. Polymers with low Tg are from alkyl acrylates such as poly (butyl acrylate) and poly (2-ethylhexyl acrylate). They are inherently soft and tacky but do not possess adequate shear strength. Polar monomers are used in co-polymerization in order to improve the adhesives' mechanical properties such as cohesion which gives an improved shear strength. Their presence increases the Tg and this may be explained by increasing dipole interaction, or enhanced hydrogen bonding. Polar groups in polymers increase intermolecular forces thus reduces free volume and increase Tg. Besides Tg, these interactions mainly affect cohesive properties. -COOH groups support intermolecular dipole dipole interactions and they are able to form hydrogen bonds with hydroxy groups which helps to increase the shear strength. In this study, synthesis of acrylic copolymers by emulsion polymerization for the application of low noise, fast drying pressure sensitive adhesives has been described and especially the effect of stabilizing monomers on noise level has been studied. It has been focused on the comparison between the adhesive performance of poly (BA-co-MMA-co-AA), poly (BA-co-MMA-co-MAA), poly (BA-co-MMA-co-AAm) and poly (BA-co-MMA-co-MAAm) by using different amount of polar co-monomers. Relatively lower noise has been obtained by MAA and MAAm. To balance the performance properties of MAA including copolymers, instead of MMA, several monomers with different Tg and polarity have been used such as EA, ACN, AAm, GMA and VAM. The performances of different polar co-monomers have been detailed on high and low surface energy substrates. An additional property such as flame retardancy has also been investigated by synthesizing copolymers containing boron acrylate and multi- functional boron methacrylates which also provides hydrophobicity and relatively higher performance on non-polar surfaces. The materials used for this research were the monomers mentioned above as butyl-acrylate (BA), methyl meth acrylate (MMA), acrylic acid (AA), methacrylic acid (MAA), acrylamide (AAm), meth-acrylamide (MAAm), acrylonitrile (ACN), vinyl acetate (VAM), ethyl acrylate (EA), hydroxyl ethyl methacrylate (HEMA), glycidyl methacrylate (Gly-MA), boron acrylate, multi-functioal boron methacrylate; surfactants; ammonium persulfate, NaHCO3 and deionized water. Solid content, pH, viscosity, surface tension, free monomer, particle size and rheology analysis have been performed by dispersion, on the other hand, swelling, Tg and performance analysis have been done by polymer film. The aim of the study is not only to investigate the influence of polar monomers on PSA performance, but also to develop an acrylic polymer for low noise packaging tape adhesives for high speed coating machines.
Graphene oxide fibers, production, characterization and utilization on the adsorption of sulfur dioxide
Fossil fuel combustion and other industrial activities cause the emission of sulfur dioxide (SO2) gas. SO2 is an air pollutant gas and a very toxic for human health and nature. Hence, cleaning of this harmful gas is an important issue. Graphene which is two-dimensional material has excellent mechanical, chemical, thermal properties, and many application areas such as energy storage devices, gas adsorption, sensing devices, and optical electronics. Further, graphene oxide (GO) is examined as a good adsorbent because of its important features such as functional groups (epoxy, carboxyl and hydroxyl) on the surface and layered structure. As a fiber form, the SO2 adsorption properties of the fibers are usually investigated on carbon fibers. This thesis seeks to investigate the adsorption capabilities of graphene oxide fibers. For this purpose, graphene oxide was produced primarily by Hummers method and graphene oxide fiber were synthesized by the wet spinning method.To see the different effects, reduction process by hydrazine hydrate, activated carbon addition, poly(vinyl) alcohol (PVA) coating and single coagulation bath application were tried on GO fibers. Monitoring of the morphology of GO fibers was carried out by SEM and AFM, also other qualitative and quantitative analyses like XRD, FTIR, Raman, conductivity and tex number were performed. TGA was used characterize the thermal properties of fibers and most importantly the surface areas of fibers were calculated by BET analysis.It has been seen that process parameters such as dispersion preparation method, pH value of dispersion, the content of coagulation bath, reduction process, and additional materials affect the final properties of graphene oxide fiber. Nonwoven based structure produced by GO fibers has an SO2 adsorption capacity itself, approximately 310-320 mg SO2/1 g of sample. However nonwoven structure produced by activated carbon doped GO fiber has 3 times higher SO2 adsorption capacity than reference GO fiber.In accordance with adsorption capacity results, activated carbon doped sample has higher BET surface area.
Fonksiyonel gruplara sahip polimerlerin sentezi ve flokülasyon ajanı olarak kullanılması
Flokülasyon prosesi maden işletmelerinde cevher zenginleştirme, kâğıt tesisleri, içecek ve gıda sektörü ile petrol çalışmaları gibi çeşitli sanayi kollarında yoğun bir şekilde kullanılmaktadır. Bu proses sonucu açığa çıkan süspansiyon içindeki kolloidal tanecikler belirli bir yük taşımaktadır. Süspansiyon kendi haline bırakıldığında belirli bir süre sonra yer çekimi etkisi ile kolloidal tanecikler yeterince büyüklerse çökecek ya da sıvı içinde askıda kalacaklardır. Çöken iri taneler ise basit bir mekanik karıştırma ile tekrar sıvı faz içinde dağılacaktır. Kolloidal tanecikler, önce yüzey yüklerinin çeşitli kimyasallarla bozulması sonucu koagüle olacak ve bu parçacıkların kimyasal bir ajan vasıtası ile daha iri topaklar oluşturması, yani aglomerasyonu ile flokülasyon gerçekleşecektir. Genelde sıvıların kolloidal parçacıklardan arıtılmasında kullanılan kimyasal malzemelere flokülasyon ajanı (flokülant) denilmektedir. Flokülasyon ajanı olarak genellikle homopolimer, blok kopolimer, aşı ya da dallı polimerler kullanılmaktadır. Bu polimerler katyonik, anyonik ya da nötr monomerlerden sentezlenerek elde edilmektedirler. Sentez aşamasında ise genelde Serbest Radikal Polimerizasyonu (SRP) kullanılmakla birlikte Kontrollü/Yaşayan Radikal Polimerleşme (KRP/YRP) teknikleri kullanılmaktadır. Bu tez çalışmasında, bu zamana kadar izlenen yöntemlerden farklı olarak fonksiyonel gruba sahip bir monomerin polimerleştirilmesi ve devamında postmodifikasyonu çalışılacaktır. Elde edilen polimerin flokülant olarak denemeleri yapılacaktır.
Polimer matrisli hibrit kompozitlerin üretimi ve karakterizasyonu
Kompozit malzemeler sahip oldukları avantajlar sayesinde havacılık, denizcilik, otomotiv, spor ve savunma sanayii gibi birçok alanda kullanılmaktadır. İki ya da daha fazla elyafın tek bir matris içerisinde birlikte kullanılmasıyla hibrit kompozitler elde edilmektedir. Hibridizasyon sayesinde kompozitin özellikleri optimize edilebilmektedir. Elyaf takviyeli kompozitlerin mekanik özelliklerinin artırılmasında kullanılan elyaf tipinin, miktarının, yönlenmesinin ve elyaf ile matris ara yüzey bağlanmasının önemi yüksektir. Bu çalışmada vakum infüzyon yöntemiyle polyester matris içerisine karbon elyaf, cam elyaf ve poliamit-66 kumaşı takviyesi ile polimer matrisli hibrit kompozit plakalar ((EC)3S, (CE)3S, (CE)3S-PA66) olarak isimlendirilmiş ve üretilmiştir. Ayrıca takviye malzemelerinin üretilen hibrit polimer kompozitlerin mekanik özelliklerine etkisi incelenmiştir. Elde edilen kompozit plakaların mekanik özelliklerini değerlendirmek için dinamik mekanik analiz (DMA), Charpy çentikli darbe testi, çekme testi, üç nokta eğme testi, çift konsol kiriş testi (DCB) ve uygulanmıştır. Test sonuçlarına göre yüksek mukavemetli karbon elyafların yük yönüne paralel olmasının çekme mukavemetinde pozitif etki yarattığı; darbe yönüne dik olan cam elyafların ise darbe mukavemetini artırdığı görülmüştür. Basma gerilmesine karşı daha dayanıklı olan cam elyafların yük yönüne dik olması üç nokta eğme testinde mukavemeti artırmıştır. Dinamik mekaniz analiz sonuçlarına göre üretim yönüne paralel karbon elyafların depolama modülünü artırdığı görülmektedir. PA66 kumaş ilavesiyle de tabakalar arası kırılma tokluğu ve darbe mukavemeti değerlerinde artış elde edilirken, diğer özelliklerde düşüş görülmüştür. Üretilen hibrit kompozitlerin üretimi ile dengelenmiş özellikler elde edilirken, maliyetten de kazanç sağlamak mümkün olabilecektir.
Pullulan bazlı polimerik yara örtüsü hazırlanması ve biyomalzemeözelliklerinin incelenmesi
Bu çalışmada, yeni bir yara örtü malzemesi olarak pullulan aşılanmış kopolimer hidrojeli hazırlandı ve karakterize edildi. Pullulan aşılanmış akrilik asit-itakonik asit kopolimer (Pu-g-p(AA-ko-IA)) hidrojeli, çapraz bağlayıcı olarak N,N'-bisakrilamid (BIS) ve baĢlatıcı olarak amonyum persülfat (APS) varlığında akrilik asit ve itakonik asitin pullulan üzerine UV kopolimerleĢme ve çapraz bağlama tekniğiyle sentezlendi. Ampisilin yüklü Pu-g-p(AA-ko-IA) hidrojeli yine aynı teknikle reaksiyon ortamına ilacın ilavesiyle hazırlandı. Hazırlanan hidrojellerin detaylı karakterizasyonu FT-IR, SEM, DSC ve TGA analizleri ile gerçekleştirildi. Pu-gp(AA-ko-IA) hidrojelinin yara örtüsü malzemesi olarak performansını ortaya çıkarmak için şişme ve in vitro sitotoksisite çalışmaları yapıldı. İlaç yüklü hidrojel için gerçekleŞtirilenin vitro ilaç salım testlerinin sonuçları, yüklenen ilacın %67'sinin 7 gün sonra Pu-g-p(AA-ko-IA) hidrojelinden salındığını gösterdi. Elde ettiğimiz sonuçlar, yüksek şişme kapasitelerine sahip Pu-g-p(AA-ko-IA) hidrojelinin yara örtüsü uygulamaları için umut verici bir aday olarak kabul edilebileceğini ortaya koymuştur.
Al/Ni(II) nikotinat / p-si ve Al/Zn(II) nikotinat / p-Si Schottky fotodiyotların elektriksel özellikleri
Yarı iletken tabanlı fotodedektörlerin üretilmesi amacıyla, Ni ve Zn merkezli nikotinat (Ni(II) nikotinat ve Zn(II) nikotinat) kompleksleri kimyasal olarak sentezlendi. Sentezlenen Ni(II) ve Zn(II) nikotinatlar, ultraviyole-görünür ışık (UV-Vis) spektrometresi ve termogravimetrik analiz (TGA) teknikleri kullanılarak analiz edildi. Sentezlenen kompleks malzemeler, Al ve p-Si arasına döner kaplama tekniği ile kaplandı ve Al/Ni(II) nikotinat/p-Si ve Al/Zn(II) nikotinat/p-Si sandviç yapıları elde edildi. Üretilen cihazların fotoelektrik karakteristikleri, karanlık ve farklı ışık şiddetleri altında fotoakım-zaman (I-t) ve akım-gerilim (I-V) ölçümleri ile analiz edildi. Yapılan ölçümler ışığında, MY/MYY diyotlar için önemli elektriksel parametreler olan seri direnç (Rs) , idealite faktörüc(n) ve bariyer yüksekliği (FBo) değerleri belirlendi. Belirli algılama, duyarlılık ve fotoduyarlılık gibi çeşitli parametreler, ışık şiddetine bağlı I-t analizi kullanılarak hesaplandı. Aynı zamanda farklı dalga boylarında aydınlatma koşulları altında gerçekleştirilen I-t ölçümleriyle harici kuantum verimliliği (EQE) değerleri hesaplandı. Sonuç olarak, Al/Ni (II) nikotinat/p-Si ve Al/Zn (II) nikotinat/p-Si yapıların fotodiyot tasarımı olarak iyi bir performansa sahip olduğu ve optoelektronik teknolojilerde kullanım için geliştirilebilir olduğu belirlendi.
Yara örtüsü uygulamaları için modifiye aljinat/jelatin/hyaluronik asit temelli hidrojellerin sentezi ve karakterizasyonu
Tez çalışması kapsamında yara örtü malzemesi olarak kullanmak amacıyla antibiyotik yüklü aljinat-jelatin-hyaluronik asit temelli hidrojeller geliştirilmiştir. Birinci aşamada, aljinat, jelatin ve hyaluronik asidin metakrilasyon reaksiyonları gerçekleştirilmiştir ve elde edilen ürünler Fourier dönüşümlü kızıl ötesi (FTIR) ve proton nükleer manyetik rezonans (1H-NMR) spektroskopisi ile karakterize edilmiştir. İkinci aşamada ise aljinat metakrilat-jelatin metakrilat (AG), aljinat metakrilat- hyaluronik asit metakrilat (AH) ve aljinat metakrilat-jelatin metakrilat-hyaluronik asit metakrilat (AGH) hidrojel formülasyonları geliştirilmiştir. Hidrojel yapılar FTIR ve taramalı elektron mikroskobu (SEM) ile incelenmiştir. Bunların yanında hidrojellerin su tutma kapasiteleri ve in vitro hidrolitik bozunma çalışmaları gerçekleştirilmiştir. Takiben tetrasiklin yüklü hidrojeller hazırlanmış ve FTIR ve diferansiyel taramalı kalorimetre (DSC) ile karakterize edilmiştir. In vitro salım çalışmaları 37 °C ve PBS ortamında gerçekleştirilmiştir. Antibakteriyel özellikleri disk difüzyon yöntemi kullanılarak S. Aureus, E. Coli ve S. Epidermidis bakterilerine karşı değerlendirilmiştir. Biyouyumluluk çalışmaları L929 hücre hattı kullanılarak 3-(4,5-dimetiltiazol-2-iI)-2,5-difenil tetrazolyum bromid (MTT) yöntemiyle belirlenmiştir. Tüm sonuçlar geliştirilen tetrasiklin içeren hidrojel yapıdaki yara örtü malzemesinin umut verici bir potansiyele sahip olduğunu göstermiştir. Anahtar Kavramlar: Hidrojel, yara örtü malzemesi, antibiyotik salımı