SYNTHESIS OF POLY (L-LACTIC ACID) BY EHYDROPOLYCONDENSATION, DETERMINATION OF SEQUENCE BY 13C NMR METHOD

Abstract

The proposed work was undertaken to synthesize high molecular weight PLA by direct polycondensation to find its better applicability in fiber
application, packaging material and commodity. However, it was reported that it was very difficult to obtain high molecular weight PLA by direct
polycondensation because of equilibrium between free acids, water and polyesters causing difficulty in removing water as a by-product. The effect
of various solvents (polar and non polar) and reaction temperatures were also investigated. In this contribution, the influence of process variables
on the molecular weight of PLA synthesized by direct polycondensation will be highlighted. We report the use of high-resolution 13C-NMR (125
MHz) spectroscopy to identify the sterosequence distribution and determine stereo specific preference for L-lactic acid addition during tin chloride
dihydrate (SnCl2.2H2O) catalyzed polymerization, and effect of various specific polymerization conditions such as temperature, duration of reaction
and the nature of solvents.