Rubber toughening of poly(lactic acid): Effect of stereocomplex formation at the rubber-matrix interface

Abstract

In this study, a series of graft copolymers poly(n-butyl acrylate)-g-poly-L-lactide (PBA-g-PLLA) and poly(n-butyl acrylate)-g-poly-D- lactide (PBA-g-PDLA) with various molecular weights and PBA/PLA ratios were prepared from the copolymerization of n-butyl acrylate and PLA macromers. The PLA macromers were prepared by ring opening polymerization of L- or D-lactide in the presence of 2-hydroxyethyl acrylate initiator. The synthesized copolymers can be used to toughen brittle PLLA by incorporating them as an elastomeric phase. Interestingly, the much tougher PLLA was obtained when the commercial PLLA was blended with 10 wt % elastomeric graft copolymer containing pendant PDLA chain. It is believed that the formation of stereocomplex between PLLA matrix and PDLA side chain in the elastomer phase differentiates it from the blend of PLLA and PBA-g-PLLA, whose side chain has the same configuration as the matrix PLLA. DSC, XRD, and TEM results support this hypothesis. Copyright © 2012 Wiley Periodicals, Inc.