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

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 ( T ODT ) 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 T ODT values, (LDL) n multiblocks of similar composition and molar mass were found to disorder at much lower temperatures ( T ODT < 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).