Synthesis and Properties of Polymers Derived from Substituted Lactic Acids

Abstract

The preparation of substituted glycolides can greatly expand the pool of monomers available for the synthesis of polyglycolides, and provide a broader range of physical properties for degradable polymers. Ethyl-, hexyl-, isobutyl-, and benzylglycolide were prepared and converted to high molecular weight polymers by ring opening polymerization in solution and using melt techniques. The polymers were clear amorphous materials with glass transition temperatures ranging from 55 to -22 °C. For alkyl-substituted poly(glycolide)s, increasing the length of a linear alkyl chain decreased Tg, while introducing branches in the alkyl chain increased Tg. Above 320 °C, the polymers thermally degrade to monomer by depolymerization. Preliminary degradation studies at 55 °C in H2O at pH 7.4 show that substituted poly(glycolide)s degrade slower than polylactide, with poly(isobutylglycolide) the most stable polymer toward hydrolysis.