Crystallization Studies on the Stereocomplexation of Poly(ʟ‐lactide) / 4‐Armed Poly(ϵ‐caprolactone‐co‐d,ʟ‐lactide)‐ block‐poly(d‐lactide) Blends

Abstract

A series of four‐armed poly(ϵ‐caprolactone‐co‐d,ʟ‐lactide)‐block‐poly(d‐lactide) (4a‐CDL‐D) copolymers with different poly(d‐lactide) (PDLA) block lengths (Mn,PDLA) were synthesized via ring opening polymerization using pentaerythritol as initiator. They were blended with poly(ʟ‐lactide) (PLLA) to improve its crystallization rate and mechanical properties. It was found that the crystallization of PLLA in the PLLA/4a‐CDL‐D blend was affected differently when Mn,PDLA changed. In the PLLA/4a‐CDL blend without PDLA blocks, the crystallization was retarded obviously because of the dilution effect of 4a‐CDL on PLLA crystallization. Interestingly, a crystallization acceleration effect was found when Mn,PDLA was 0.5k although no stereocomplex (SC) crystallites existed. When Mn,PDLA was 1k or higher (1.5k and 2k), SC crystallites could be formed in the PLLA/4a‐CDL‐D blends. However, when Mn,PDLA was 1k or 1.5 k, the formation of SC crystallites was difficult and they showed weaker acceleration effect on PLLA crystallization. While when Mn,PDLA was 2k, the crystallization of PLLA was accelerated markedly due to the significant increase of nucleation sites. At last, these blends had longer elongation at breaks than neat‐PLLA. This work provided a novel method for the acceleration of PLLA crystallization by adjusting the PDLA chain length in PLLA blends.