A study of swelling process of hydrogels with fluorescence spectrometer and computer modelling

In this thesis study, we studied hdyrogels which were astonishing because of the absorbing huge amount of water or biological liquids. They have become a research topic in various fields. We can see numerable studies about hydrogels in the corresponding literature. Especially they are being used to develop contact lenses, disposable diapers, artificial bone substitutes... etc. Another remarkable research area is the pharmaceutical industry. Hydrogels are being widely used as drug delivery systems in this field as well. First of all, the study of the swelling of hydrogels with fast transient fluorescence technique (FTRF) is aimed to be conducted for the first time. Other one is the transformation of pyrene from hydrophobicity to hydrophilicity. Pyrene is used as an agent molecule for this technique. Another purpose is the calculation of cooperative diffusion coefficient (Dc) from the flurorescence and gravimetric experiments. Lastly, we wanted to develop a computer programme for the calculation of cooperative diffusion coefficient Dc automatically, based on the experimental outcomes.Also this programme will have include a small part for the calculation of gel contents automatically. We examined the hydrogel's swelling process by using fast transient fluorescence technique (FTRF). This study is done for the first time for hydrogels. It is not possible for pyrene as shown in the previous studies because of its hydrophobic feature. However, we found a way that make pyrene hydrophilic and use it as our aromatic molecule. Fast transient fluorescence measurements were performed with a Photon Technology International (PTI). This technique uses a strobe master system (SMS) to measure lifetimes. As aromatic molecule, Pyrene molecules were excited to fluorescence at 345nm and fluorescence decay profiles were obtain at 395nm in swelling experiments. In order to find the lifetime of Pyrene molecules during the network formation, the fluorescence decays were fit to double exponentials. Hydrogel samples were obtained from acrylamide (AAm) with various N,N'-methylenebisacrylamide (BIS) contents as cross-linker. In addition, amonium persulfate (APS) was used as an initiator by free-radical cross-linking copolymerization in water. All the Polyacrylamide (PAAm) gels were dried before using for swelling experiments. We believe that we succeed to transformation of pyrene from hydrophobicity to hydrophilicity. Thereupon we could use it as aromatic molecule. For FTRF technique, this is the first. As we expected, when BIS values increase, Dc values dicrease. These results were obtained from both fluorescence and gravimetric experiments. As a result, it was observed cage effect of Pyrene molecules. When the cross-linker quantity is raise, the network of inter-molecules is get close up. In consequence of this, solvent uptake is get hard. Based on the outcomes of fluorescence measurements, it was developed a programme which was tested and is convinced to work properly. For the future, we intend to extend this programme for a wide usage and redo this work for different ph values.