Synthesis and modification by inverse electron demand Diels-Alder reaction of poly(styrene-co-acrylonitrile) with tetrazine, and synthesis of poly(ɛ-caprolactone-b-ethylene glycol methyl ether) by copper-catalyzed azide-alkyne cycloaddition reaction

In the first stage of this study, poly(ɛ-caprolactone-b-ethylene glycol methyl ether) [poly(CL-b-mEG)] block copolymers were synthesized using azide-terminated poly(ɛ-caprolactone) ester (PCL-N3) and polyethylene glycol methyl ether propargyl (mPEG-propargyl) via "click" chemistry method. For this purpose, firstly 2-[2-(2-azidoethoxy)ethoxy]ethanol was obtained from the reaction of 2-[2-(2-chloroethoxy)ethoxy]ethanol with sodium azide. PCL-N3 was synthesized by ring-opening polymerization of ɛ-caprolactone with 2-[2-(2-azidoethoxy)ethoxy]ethanol. mPEG-propargyl was synthesized by the reaction of polyethylene glycol methyl ether (mPEG) with different molecular weights (Mn~5000 g.mol-1 and Mn~2000 g.mol-1) and propargyl bromide / chloride. Then, poly(CL-b-mEG) block copolymers were obtained using PCL-N3 and mPEG-propargyl by the "click" chemistry method. The effect of the concentration on the block copolymer formation was investigated. In the second stage of the study, poly(styrene-co-acrylonitrile) [P(SAN)] copolymer was obtained by using styrene and acrylonitrile monomers via free radical polymerization. The tetrazine groups were formed in P(SAN) copolymer backbone by using 2-fluorobenzyl cyanide, hydrazine hydrate, zinc iodide as the catalyst, and then sodium nitrile. The tetrazine groups formed in the copolymer backbone were modified using trans-cyclooctenol by the Inverse Electron Demand Diels-Alder (IEDDA) reaction. The spectroscopic properties of the obtained products were determined by Fourier transform infrared and proton nuclear magnetic resonance and the thermal properties of them were determined by thermogravimetric analysis and differential scanning calorimetry techniques. The average molecular weights of the synthesized polymers were defined by using gel permeation chromatography and static light scattering methods. Morphological properties were examined with scanning electron microscope.