Totally biodegradable poly(trimethylene carbonate/glycolide-block-L-lactide/glycolide) copolymers: synthesis, characterization and enzyme-catalyzed degradation behavior

The macroinitiator of poly(1,3-trimethylene carbonate-ran-glycolide) (P(TMC-ran-GA)) copolymers terminated with hydroxyl groups were synthesized by ring-opening polymerization (ROP) at 120 degrees C for 12 h. Then, the novel block copolymers consisting of P(TMC-ran-GA) segments bonding with L-lactide (LLA) and glycolide (GA) random copolymerization segments were prepared. The poly(TMC/GA-block-LLA/GA)) block copolymers were synthesized by ROP in bulk at 130 degrees C with high (M-n) over bar, (above 2.0 x 10(5) Da). Such kind of block copolymers composed of P(TMC-ran-GA) and P(LLA-ran-GA) segments show good mechanical properties and adjustable degradation rate. The molecular structures of block copolymers were characterized by GPC, FTIR, and H-1 NMR. Chain microstructure analysis was performed in detail with C-13 NMR spectroscopy. The effect of GA units content on thermal behaviors, mechanical properties as well as biodegradability of copolymers was investigated by DSC, XRD, stress-strain measurements and enzymatic degradation tested in comparison with corresponding block copolymers P(TMC-block-LLA/GA). The results shown that amorphous P(TMC-ran-GA) segments significantly improve the flexibility of block copolymers. The incorporation of GA units strongly decreases the crystallization ability of LLA segment within copolymers due to more random LLA-GA sequence and shorter average LLA block length. Meanwhile, the tensile strength of material and flexibility are significantly improved with the raising GA units content. The enzymatic degradation rate is also accelerated with the increase GA unit content. Thus, the biodegradable block copolymers with unique molecular structure and modifiable properties are promising new materials for biomedical applications.