Impact of Crystallization Mode on Performance of Aliphatic Polyester Thermoplastic Elastomers

Sustainable thermoplastic elastomers (TPEs) containing crystallizable poly(lactide) (PLA) end blocks can undergo different modes of crystallization that include crystallization induced microphase separation, confined crystallization, and breakout crystallization. These modes have a significant impact on the mechanical properties of the resultant materials. To explore the interplay between crystallization and block polymer ordering, we exploit the stereochemical diversity of PLA to create a series of PLA-b-poly(γ-methyl-ε-caprolactone)-b-PLA linear triblock polymers with stereoblock, stereopure, and stereorandom PLA end blocks. By maintaining a consistent overall molar mass, we directly compare the impact of end block stereochemistry on TPE material performance. Through tensile, hysteresis, and stress relaxation analyses we determined that the highest performing samples were comprised of stereoblock PLA end blocks that exhibited confined crystallization. This understanding of the interplay between crystallization and block polymer ordering informs the design of next-generation high-performance TPEs that can be sourced from renewable feedstocks and are industrially compostable.