ABA Triblock Copolyesters Composed of Poly(L-lactide) A Hard Blocks: Long Chain Aliphatic Polyesters as B Soft Midblocks

Abstract

A series of triblock copolyesters were produced by ring-opening polymerization of l-lactide initiated by the dihydroxy-terminated poly(alkylene dodecanedioate)s as macroinitiators. The dihydroxy-terminated poly(alkylene dodecanedioate)s as low melting blocks were prepared by using 1,12-dodecanedioic acid and methyl substituted aliphatic diols. The influence of the different polyesters middle block on microstructure, thermal, crystallization and tensile properties of the triblock copolyesters was investigated. It was found that the poly(alkylene dodecanedioate)s containing methyl substitutions still exhibited crystallization and melting behavior, but the crystallization ability decreased when compared with linear poly(alkylene dodecanedioate). The diffraction peaks of soft and hard segments, measured by WAXD, showed a gentle trend after copolymerization. Through the TGA test, the results showed that thermal stability of the triblock polyesters was improved. Tensile tests exhibited that the elongation at break was improved significantly, with the highest elongation at break reaching 400%, while the tensile strength of triblock copolyesters decreased slightly compared with polylactide. The correlation between the middle block structures and their physical properties was explored and discussed.