Synthetic pathways enables the design of functionalized poly(lactic acid) with pendant mercapto groups

Abstract

Functionalized poly(lactic acid) having sulfur-protected groups along the chain have been synthesized with the ultimate aim to obtain materials for reversible and degradable self-assembly systems. The first step in the synthesis was the preparation of hydroxy-(4-methyl-phenylsulfanyl)-propionic acid and hydroxy-(tritylsulfanyl)-propionic acid. These sulfur-functionalized hydroxy acids were subsequently used as comonomers in the condensation polymerization of lactic acid producing functionalized polyesters with thio-protected groups along the chain. The ratio of functionalized hydroxyl-acid in the copolymer was determined by the feed ratio. The polyesters obtained were amorphous and size exclusion chromatography analysis showed a monomodal distribution. When treated with iodine, the polyesters chains bearing the tritylsulfanyl side groups assembled with the formation of S-S bridges and the molecular weight increased accordingly. © 2011 Wiley Periodicals, Inc.