Preperation of polymer nanocomposites via metal free click reactions

To achieve the desired final properties of nanocomposite materials, important parameters such as careful selection of the polymer matrix and appropriate nanofiller considering the entire nanocomposite system, interactions between the components and their morphologies should be considered. Chemical modification or post-modifications may be required to impart the desired properties onto the components or resulting nanocomposites. In this sense, in last decades, the click chemistry reactions have been drawn attention about improving of the properties of polymer nanocomposites. These reactions have advantages such as high reaction efficiency, mild reaction conditions, no by-product formation, orthogonal and stereospecific reaction and functional group diversity. Furthermore, the quantitative efficiency, tolerance to several functional groups and reaction conditions are significant properties in preparation of nanocomposite. In addition, click chemistry reactions such as electron deficient alkyn-azide click reactions (AAC), Diels-Alder (DA) reactions which can be performed without metal catalysts, are quite remarkable for toxicity sensitivity applications. In this thesis, it is aimed to prepare three different polymeric nanocomposites to improve their chemical, thermal, mechanical and morphological properties via various click reactions. In the first study, a new type thermoset hybrid network polymeric nanocomposite was synthesized by copper free 1,3 dipolar cycloaddition reaction between aliphatic polyester containing electron-deficient alkyne in its main chain and a multifunctional azido-polyhedral oligomeric silsesquioxane (POSS-N3). The chemical structures of the synthesized nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR) and scanning electron microscopy - energy distribution spectroscopy (SEM-EDS). Thermal, mechanical and morphological properties were also analysed by thermogravimetric analysis (TGA), tensile test and scanning electron microscopy, respectively. In the second study, poly(ε-caprolactone)/clay nanocomposites were prepared by Diels–Alder (DA) click reaction of poly(ε-caprolactone) containing maleimide end group and furan-functionalized montmorillonite (MMT). First, the modification of MMT clay with furan and ring-opening polymerization of ε caprolactone by initiating masked maleimide group-containing alcohol were performed. Subsequently, the retro-Diels-Alder (r-DA) reaction was carried out to obtain maleimide terminated poly (ε-caprolactone) (PCL). Characterizations of PCL/MMT nanocomposite materials were performed by TGA, FT-IR, X-ray diffraction spectroscopy (XRD), transmission electron microscope (TEM) analysis. In the third study, as a new approach to improve the properties of PVC, POSS nanoparticles were covalently bonded to poly (vinyl chloride) (PVC) chains via the DA click reaction by post-polymerization modification method. The neat PVC and aminopropyl isobutyl POSS (POSS-A) are functionalized with furfuryl alcohol and DA adduct, respectively, for the DA click reaction. The synthesized nanocomposites contain different mole ratios (mole/mole of 1, 2 and 4%) of POSS nanoparticles. The chemical, mechanical, thermal and morphological properties of the obtained nanocomposites were characterized by FT-IR, 1H-NMR, tensile test, DSC, TGA, SEM and TEM.