The random copolymers of glutamic acid(LG)and aspartic acid(ASP),poly(LG-co-ASP),with designed compositions could be successfully synthesized via combination of N-carboxyanhydride ring opening copolymerization with debenzylation.Ring opening copolymerizations ofγ-benzyl-L-glutamate N-carboxyanhydride(BLG-NCA)andβ-benzyl-Laspartate N-carboxyanhydride(BLA-NCA)were carried out by using different amines including triethylamine(TEA),diethylamine,n-hexylamine(NHA),triphenylamine,diphenylamine or aniline as initiators.All the 6 amines were highly efficient to get well-defined poly(BLG-co-BLA)copolymers with designed compositions although the polymerizations proceeded via different mechanisms(normal amine mechanism or/and activated monomer mechanism),which are based on chemical structure of amines.The molecular weights of poly(BLG-co-BLA)copolymers could be mediated by both TEA concentration and polymerization time.Then,debenzylation of poly(BLG-co-BLA)copolymers was conducted to prepare the corresponding hydrophilic random copolymers of poly(LG-co-ASP)withα-subunit structure in ASP structural units.The contents of LG structural units in poly(LG-co-ASP)copolymers matched with those of BLG-NCA in NCA-monomer feeds in ring opening copolymerizations initiated by NHA or TEA and were closed to the theoretical line.The diblock copolymer of poly(BLG-b-BLA)could also be synthesized via living NCA ring opening copolymerization by sequential addition of BLGNCA and BLA-NCA.
