Thermoplastic elastomers (TPEs) based on polystyrene (PS) are commonplace in society. The elastomeric properties of these materials are often sacrificed to increase mechanical properties such as stiffness, strength, and toughness. We sought to produce stiff, strong, and tough TPEs that retain their elastomeric properties by shifting the lamellar phase boundary toward higher PS content. By precisely controlling the molecular weight distribution (MWD) shape of one PS block in polystyrene-block-polyisoprene-block-polystyrene (SIS), we produced elastomeric continuous phase TPEs at atypically high PS volume fractions, shifting the lamellar phase boundary from 0.33 in triblocks with a narrow MWD PS block to ∼0.39 in triblocks with a broadened MWD PS block. Furthermore, we observed hexagonal/lamellar phase coexistence at a PS volume fraction of 0.39 when the MWD shape of the first PS block was asymmetric. These materials exhibit enhanced mechanical properties consistent with high volume fractions of PS and elastomeric properties consistent with continuous morphologies.

Taking advantage of molecular weight distributions shape, we report a simple and efficient approach for predictably tuning material properties for thermoplastic elastomers.

Reversible addition-fragmentation chain-transfer (RAFT) polymerizations are one of the most versatile and powerful polymerization techniques for the synthesis of complex macromolecular architectures. While RAFT polymerizations often give polymers with narrow...

Thermoplastics and thermoplastic elastomers compose roughly 80 percent of all polymeric materials manufactured today and play an important role in numerous sectors of modern society. While the effects of molecular weight and dispersity (Ð) on the tensile and rheological properties of these materials are well-known, only recent studies have evidenced the profound influence of the shape of the molecular weight distribution (MWD) on polymer properties. This development is largely due to the emergence of new synthetic strategies to control higher moments of the MWD. In this Perspective, we describe recent advancements by our group in understanding the effect of MWD shape on the mechanical and rheological properties of thermoplastics and thermoplastic elastomers. We highlight means to exploit MWD shape for improved processability and performance and discuss future directions in this field.

Cationic polymerization enables production of sustainable thermoplastic elastomers constructed from renewable vinyl ethers and -p-methoxystyrene with properties consistent with their petroleum-derived counterparts.