Hybrid Soft Segments Boost the Development of Ultratough Thermoplastic Elastomers with Tunable Hardness

Abstract The hardness of thermoplastic elastomers (TPEs) significantly influences their suitability for various applications, but traditionally, enhancing hardness reduces toughness. Herein a method is introduced that leverages hybrid soft segments to fine‐tune the hardness of TPEs without compromising their exceptional toughness. Through the selective copolymerization of polytetramethylene ether glycols (PTMEGs) at various molecular weights, supramolecular poly(urethane‐urea) TPEs are molecularly engineered to cover a wide spectrum of hardness while retaining good toughness. It is achieved through the formation of graded functional zones—densely packed for enhanced hardness and strength, and loosely packed for greater extensibility and toughness—driven by variations in PTMEG chain length and mismatched supramolecular interactions. Through the establishment and systematic investigation of a TPE library, the intricate interplay between design, structure, and performance of these materials is elucidated, refining the optimization techniques. The TPEs demonstrate exceptional mechanical properties, including a variant with a Shore hardness of 86A and a toughness of 819 MJ m −3 , alongside a softer variant with a 59A hardness and a 786 MJ m −3 toughness. The innovation extends to a scalable solvent‐based TPE production line, promising widespread industrial application. This advancement reimagines the potential of high‐performance TPEs and composites, offering versatile materials for demanding applications.