Skin-inspired bio-based polyurethane elastomers with dual-soft-segment-regulated reversible associations for flexible strain sensors.

Flexible polymeric materials for wearable electronics are expected to maintain mechanical robustness, large-deformation adaptability, elastic recovery, and stable sensing performance under repeated deformation. However, these requirements are difficult to satisfy simultaneously because strong interchain interactions improve load bearing but usually restrict chain mobility, whereas highly flexible networks often lack sufficient mechanical strength. Herein, a dual-soft-segment regulation strategy is proposed to construct bio-based polyurethane elastomers with an optimized amorphous association network. By regulating the soft-segment ratio, the concentrated strong associations were redistributed into a balanced interaction environment consisting of moderate urea/urethane hydrogen bonds and carbonate-related polar associations. The optimized BCPU3 elastomer exhibited a tensile strength of 47.8 MPa, an elongation at break of 1528.5%, and a toughness of 312.5 MJ m-3, while maintaining pronounced hysteretic recovery and time-dependent network reconstruction after large deformation. Furthermore, BCPULi-2 was used as an ion-conductive adhesive layer to construct a sandwich-structured strain sensor with fast, stable, and durable strain-sensing performance, enabling reliable monitoring of human motions, gesture recognition, and external mechanical stimuli. This work provides a soft-segment engineering strategy for developing high-performance bio-based polyurethane elastomers and mechanically reliable flexible sensing devices.