SYNTHESIS AND CHARACTERIZATION OF POLY(L-GLUTAMIC ACID-co-L-ASPARTIC ACID)

 Poly(amino acid) has been widely utilized in drug delivery, tissue engineering and biomedical materials. The biomaterials based on poly(glutamic acid) are usually modified via copolymerization with other monomers such as L-aspartic acid to improve the uncontrolled degradation rate. The ring-opening homo- and co-polymerization of γ-benzyl-L-glutamate N-carboxyanhydride (BLG-NCA) and β-benzyl-L-aspartate N-carboxyanhydride (BLA-NCA) were carried out in solution by using triethylamine (TEA) as initiator. The BLG-NCA homopolymerization could take place even at －30^οC and molecular weight of poly(γ-benzyl-L-glutamate) decreased with increasing polymerization temperature. The BLA-NCA polymerization did not occur at －10^οC and was needed to be carried out at 25^οC to improve the polymerization. Poly(γ-benzyl-L-glutamate) and poly(β-benzyl-L-aspartate) with unimodal molecular weigh distribution and weight average molecular weight (M_w) of 32100 and 4000 could be obtained at 25^οC. The copolymers of γ-benzyl L-glutamate and β-benzyl L-aspartate with unimodal molecular weight distribution and M_w ranging from 5600 to 24600 could be prepared. The useful copolymers of poly(L-glutamic acid-co-L-aspartic acid) were further prepared by removal of benzyl groups.