Synthesis and characterization of degradable triarm low unsaturated poly(propylene oxide)-block-polylactide copolymers

摘要

A series of novel degradable triarm poly-(propylene oxide)-block- polylactide (PPO-b-PLA) copolymers was synthesized by ring-opening polymerization of L-lactide (LLA) or D,L-lactide (DLLA) using low unsaturated PPO triols as macromolecular initiator. The chemical structures of the resulting copolymers were characterized by Fourier transform infrared (FTIR), gel permeation chromatography (GPC), and proton nuclear magnetic resonance (1H-NMR) spectroscopy. Combination of FTIR, GPC, and NMR results confirmed the formation of PPO-b-PLA copolymers. One glass transition was observed by differential scanning calorimetry (DSC), suggesting good miscibility between PPO and PLA segments in the copolymers. DSC and wide-angle X-ray diffraction demonstrated that PPO-b-PLLA copolymers were semicrystalline materials, and the crystallinity increased with increasing the PLLA content. In contrast, PPO-b-PDLLA copolymers were totally amorphous. The PPO-b-PLA copolymers exhibited improved thermal stability when compared with PPO polyols according to thermogravimetric analysis. The thermal degradation behavior of the copolymers depended on the composition. Polyurethane foams were prepared by crosslinking PPO and PPO-b-PLA copolymers using isocyanate. Alkaline degradation of the foams was investigated in 10 wt/vol % NaOH at 80°. The results show that the novel PPO-b-PLA copolymers could be promising as degradable polymeric materials.