STAR-LIKE LACTIC ACID OLIGOMERS IN THE SYNTHESIS OF LACTIDE

摘要

Poly(lactic acid) can be produced by the ring opening polymerization of lactide, or by the direct polycondensation of lactic acid. the second route does not produce polymers having high molecular weights due to the presence of water. Furthermore, during the polycondensation, the molecular weight of poly(lactic acid) is reduced by depolymerization where the lactide is formed. The yield of depolymerization reaction depends on the kind of catalyst. The purpose of this study was to prepare low molecular weight star-like lactic acid oligomers and then use them as prepolymers in the synthesis of lactide. All reactions were carried out in the melt under reduced pressure at 190 ℃ for 8 h in the presence of different catalysts (0.2 mol % of L-lactic acid). The lactides were characterized by nuclear magnetic resonance and gas chromatography. The lactic acid, lactic acid oligomers, water and meso-lactide contents were observed. The molecular weights of prepolymers and final polymerss were determined by GPC and were also calculated by using the peak integrals of ~1H NMR spectra. This work was financially supported by the National Centre for Research and Development (PBS2/A1/12/2013; ID210366; acronym LACMAN).