SYNTHESIS AND CHARACTERIZATION OF ELECTROACTIVE GRAFT COPOLYMER OF POLY( L-GLUTAMIC ACID)-g-ANILINE TETRAMER

Novel electroactive and biodegradable graft copolymers with aniline tetramer side chains were synthesized by conversing the side carboxyl groups of poly(L-glutamic acid) to active N-oxysuccinimide ester, which can be easily substituted by amino compounds. The main chain of grafting copolymer, poly(L-glutamic acid) was recognized as a biodegradable polymer, and the aniline tetramer side chain, which is similar with polyaniline in electrical chemical properties, enabled the copolymer to gain or lose electron reversibly, i. e. electroactivity. The chemical structures of the copolymers were confirmed by (1)H-NMR, UV-Vis spectrum and elemental analysis. The copolymer can be dissolved in DMF, DMSO or alkaline aqueous solution. The UV-Vis spectrum of the copolymer was measured in DMF at different buffer pH values. The aniline tetramer side chain can be oxided to its emeraldine state in the presence of oxidant and doped by protonic acid. The cyclic voltammogram of the copolymer, measured in 1 mol/L HCl aqueous solution,showed that there were two pairs of reversible redox peaks, which correspond to two redox processes. These characters indicated that the graft copolymer showed a good electroactivity. The graft ratio of aniline tetramer was confirmed by both element analysis method and quantitative UV absorbance of the copolymer in its leucoemeraldine state. The graft ratio could reach to upon 40% by appropriate feed ratio, which meant a higher weight percentage of electroactive units compared with those block copolymers previously reported. A new route to build both electroactive and biodegradable polymers was reported, which may have potential application in nerve tissue engineering and some other aspects of biological researches.