Synthesis of high molecular weight poly(L-lactic acid) and poly(D-lactic acid) with improved thermal stability via melt/solid polycondensation catalyzed by biogenic creatinine

摘要

Stereoregular high polymers of poly(L-lactic acid) (PLLA) (M_w 1.2 × 10~5, isotacticity 96.0%) and poly(Dlactic acid) (PDLA) (M_w 1.0 × 10~5, isotacticity 98.6%) were successfully synthesized via melt/solid polycondensation (MP/SSP) using a biogenic catalyst creatinine (CR). The follow-up monitor of the polycondensation products with ~(13)C NMR technique revealed that the polymerization of MP/SSP proceeded in a stereochemical controlled way throughout the whole process as evidenced by the constant high values of isotacticity (97.8e99.4%) of produced polymers. Thermogravimetric analysis demonstrated that the decomposition temperatures (T_(d, init) 324.3 °C, T_(d, 5%) 347.0 °C, T_(d, max) 400.2 °C) of PLLA synthesized with catalyst CR are over 100 °C above those of PLLA synthesized with catalyst SnCl_2·2H_2O.