Ring-opening precipitation polymerization of poly(D,L-lactide-co-glycolide) in supercritical carbon dioxide

The biodegradable polymer poly(D,L-lactide-co-glycolide) was synthesized by a ring-opening precipitation polymerization in supercritical CO2 using sta nnous octoate as initiator. Following polymerization, unreacted monomer was removed by supercritical fluid extraction and the polymer was recovered as a porous solid upon depressurization of the CO2 phase. The lactide to glyc olide ratio of the polymer was determined to be 70.7:29.3 using C-13 NMR sp ectroscopy. The weight-average molecular weight of the product was measured to be 3 500, with a polydispersity of 1.4 using gel permeation chromatogra phy.