Crystallization and Mechanical Properties of Poly(l-lactide)-Based Rubbery/Semicrystalline Multiblock Copolymers

Abstract

The crystallization and mechanical properties of triblock and multiblock copolymers containing 70 vol % semicrystalline poly(l-lactide) (L) and 30 vol % rubbery poly(ethylene-co-ethylene) (E/EE) were investigated. The multiblock copolymer was synthesized directly from the triblock copolymer (denoted LE/EEL). Specifically, the dihydroxyl-terminated LE/EEL served as a macromonomer in a step-growth polymerization in which stoichiometric quantities of sebacoyl chloride were added, resulting in (LE/EEL)⟨3.6⟩, a multiblock copolymer with an average of 3.6 triblock copolymer units connected together. Additionally, triblock and multiblock copolymers were blended together in order to systematically tune ⟨n⟩ and uncover the role of block number on properties. Dynamic mechanical analysis (DMA) indicated that despite differences in ⟨n⟩, all samples had an order-to-disorder transition temperature TODT ≈ 190 °C, which is above the melting temperature (Tm) of poly(l-lactide). Small-angle X-ray scattering measurements (S...