Enhancement of molecular weight of L-lactic acid polycondensates under vacuum in solid state

Abstract

Enhancement of L-lactic acid polycondensates by involving of postpolycondensation reactions in solid state under vacuum and catalyzed by stannous 2-ethylhexanoate were studied in the presented work. The catalyst was used only in postpolycondensation step. An effect of the catalyst concentration and postpolycondensation reaction time on resulting properties of poly(lactic acid) was studied by gel permeation chromatography. Fourier transform infrared spectroscopy and differential scanning calorimetry. Results show significant enhancement of molecular weight in case of the systems containing 2 wt. % of the catalyst due to the postpolycondensation procedure (M-W similar to 91.0 kg/mol; i.e. 1655 % after 24 hours). However, further progress can be assumed with increasing reaction time. This enhancement of poly(lactic acid) molecular weight had a response corresponding to changes of both physico-chemical and thermal properties of the solid state postpolycondensation products.