Synthesis and characterization of novel copolymers containing pendant amine functional groups based on D, L-lactide, glycolide and poly(peg-co-L-aspartic acid)

Poly (poly (ethylene glycol) -co-L-aspartic acid) (PEG-ASP), alternating prepolymer was first prepared by the solution polycondensation from N-(benzyloxycarbonyl)-L-aspartic acid anhydride and poly(ethylene glycol). Then, the novel PLGA-( PEG-ASP). copolymers with pendant amine functional groups were synthesized by bulk ring-opening copolymerization of D, L-LA with GA using tin octoate(Sn(Oct)(2)) as a catalyst, and (PEG-ASP)(n) prepolymer as a co-initiator. The structure and properties of the novel copolymers were studied by GPC, Fr-IR,H-1-NMR and DSC, etc. Results showed that the PLGA- (PEG-ASP). copolymers were typical amorphous polymers. The content of ( PEG-ASP), prepolymer had significant influence on the properties of the copolymers. The hydrophilicity of the copolymers was improved and the value of the glass transition temperature(T-g) decreased as the content of the prepolymer increased. The benzyloxycarbonyl (CBz) protecting groups of the copolymer were totally removed by catalytic transfer hydrogenation using palladium over activated carbon (5 wt%) as a catalyst and H-2 as an effective hydrogen donor. The molecular weight,the value of T-g and hydrophilicity of the copolymer were somewhat increased as the CBz protecting groups were removed.