HyperMacs to HyperBlocks: A Novel Class of Branched Thermoplastic Elastomer

We demonstrate here the great versatility of the macromonomer approach for the synthesis of long chain hyperbranched polymers (HyperMacs) and describe the synthesis of HyperMacs from polybutadiene and poly(methyl methacrylate) using analogous yet modified synthetic strategies. Furthermore, we report the synthesis, morphology, and mechanical properties of an entirely new class of HyperMacs—HyperBlocks—prepared from the coupling of polystyrene−polyisoprene−polystyrene triblock copolymer macromonomers. Transmission electron microscopy (TEM) studies show that these unconventional block copolymers undergo microphase separation, but the resulting morphologies lack any long-range order. Tensile testing shows that these materials offer promise as a new class of branched thermoplastic elastomer (TPE). Finally, blends of HyperBlock (10%) with a commercial linear TPE produced by Kraton show both enhanced ultimate tensile stress and elongation at break.