Highly Tough, Notch‐Insensitive, and Fast Self‐Healing Thermoplastic Polyurethane Elastomers by Tailored Soft Segment Design

Achieving toughness, notch insensitivity, and self-healing within a single thermoplastic polyurethane (TPU) system is challenging. Hard domains formed by hydrogen-bonded urethane linkages provide mechanical strength but limit the chain mobility needed for healing, while soft domains enable elasticity but are more vulnerable to damage. We propose a soft-segment modification strategy that incorporates α,ω-hydroxyl end-functionalized polyacrylates into conventional TPU structures. Unlike our previous systems based on linear-alkyl acrylates (i.e., n-butyl acrylate), introducing branched-alkyl acrylic soft segments (i.e., 2-ethylhexyl acrylate) generate side-chain architectures whose segmental dynamics respond more sensitively to temperature. This enhanced thermal responsiveness promotes thermally activated chain mobility and more uniform stress distribution, all without compromising the mechanical contribution of the hard domains. As a result, the acrylic TPUs display high toughness (186 MJ·m^- ³), stable notch performance (fracture energy >197 kJ·m^- ² at elongations above 900%), and practical self-healing (∼90% recovery at 45°C within 3 h). These findings highlight that branched polyacrylate-based soft-segment engineering offers a balanced pathway to mechanically robust and adaptable TPU elastomers.