Thermal stability of copolymer derived from L-lactic acid and poly(tetramethylene) glycol through direct polycondensation

The thermogravimetric analysis (TG) of triblock copolymers (PLAG) based on poly(l-lactic acid) (PLLA) and poly(tetramethylene) glycol (PTMEG) segments with different PTMEG content and catalyst concentration was conducted. The thermal degradation behaviors of copolymers were determined by thermogravimetric analysis and the results are also confirmed by hydrogen nuclear magnetic resonance spectrometry (H-1 NMR). The thermal stability of PLA-based copolymer is improved with decreasing use level of Sn catalyst and short-chain molecules with hydroxyl and carboxyl end group also have a significant effect on the thermal degradation of chain-extended products of copolymer (PLAE). PLAE-10 with 0.5 wt% catalyst shows two main decomposition kinetic mechanisms. On the other hand, PLAE-10 with 0.05 wt% catalyst mainly undergoes Sn-catalyzed selective depolymerisation. Moreover, the PTMEG segments in PLAEs seem to increase the mobility of the Sn salt moiety in PLAEs and the activation energy (E (a)) decreases with increasing the PTMEG content in PLAEs.