Synthesis and Melt Processing of Sustainable Poly(ε-decalactone)-<i>block</i>-Poly(lactide) Multiblock Thermoplastic Elastomers

Abstract

A one-pot, one-catalyst, sequential ring-opening transesterification polymerization (ROTEP) was used to prepare fully renewable amorphous poly(d,l-lactide)–poly(ε-decalactone)–poly(d,l-lactide) (LDL) triblock polymers. These α,ω hydroxy-telechelic polymers were subsequently coupled to prepare linear alternating (LDL)n multiblock polymers. Differential scanning calorimetry (DSC) and small-angle X-ray scattering (SAXS) indicated microphase separation into two domains in both the triblock and multiblock architectures. The temperature dependent Flory–Huggins interaction parameter for this system, χ(T) = 69.1/T – 0.072, was estimated from the experimentally determined order–disorder transition temperature (TODT) values of four symmetric LDL triblock polymers. Uniaxial extension tests revealed a dramatic dependence of the room-temperature mechanical properties on overall molar mass. Additionally, coupling low molar mass LDL triblocks to prepare (LDL)n multiblocks led to substantial increases in the ultimate elongation and tensile stress at break. Compared to high molar mass triblocks with inaccessible TODT values, (LDL)n multiblocks of similar composition and molar mass were found to disorder at much lower temperatures (TODT < 150 °C). Because of this, it was possible to process (LDL)n using injection molding. The simple synthetic procedure and melt processability of the (LDL)n multiblock polymers make these multiblocks attractive as renewable thermoplastic elastomers (TPEs).