POLYMERIZATION OF GLYCOLIDE PROMOTED BY OMEGA-AL-ALKOXIDE POLY(EPSILON-CAPROLACTONE) MACROINITIATORS AND FORMATION OF STABLE COLLOIDAL DISPERSIONS

Block polymerization of glycolide (GA) and epsilon-caprolactone (epsilon-CL) has been initiated with aluminum alkoxides, such as Al(O(i)Pr)3 and Et2AlOCH2X (where X = -CH2-Br and -CH2O-C(O)-C(Me)=CH2), in THF at 40-degrees-C. Structure and composition of block copolyesters have been characterized with respect to the molecular weight by NMR spectroscopy and thermal analysis. Copolymerization is typically living, so that block copolyesters have been synthesized with predictable molecular weight and composition. The inherent insolubility of polyglycolide block is responsible for the heterogeneity of the polymerization medium and formation of stable, non-aqueous colloidal dispersions. This effect is especially pronounced at high GA/epsilon-CL molar ratios. Colloidal dispersions have been analyzed by transmission electron microscopy (TEM) and photocorrelation spectroscopy (PCS).