High molecular weight poly(L-lactide) and its microsphere synthesized in the supercritical dimethyl ether

Abstract

The ring-opening polymerization of L-lactide initiated by stannous octoate was carried out in supercritical dimethylether(scDME) at various reaction conditions (time and temperature). The monomer conversion increased to ca. 90% on increasing the reaction time to 1hr. The molecular weight of the poly(L-lactide)(PLLA) also increased to ca. 160,000 g.mol(-1) over the same period. increasing reaction temperature from 118 to 135 degrees C or reaction pressure from 280 to 520 bar resulted in increased monomer conversion and molecular weight. After the polymerization, PLLA microspheres were prepared in situ by using a continuous supercritical anti-solvent process without residual organic solvent.