Lithium Salt Enhancement Strategy for Dynamic Polyurethane‐Urea: Achieving Ion‐Conductive Elastomer with Superior Mechanical Properties

ABSTRACT Ion‐conductive elastomers (ICEs) have broad application prospects in wearable devices, human‐machine interaction, and other fields due to their excellent multi‐functional sensing properties. However, the low mechanical properties of conventional ICEs severely limit their practical applications. Herein, a high‐performance polyurethane‐urea‐based ion‐conductive elastomer (PUUICE) is developed, and a lithium salt enhancement strategy is proposed to achieve ultrahigh mechanical robustness. The effects of lithium bis(trifluoromethanesulfonic)imide (LiTFSI) and polyethylene glycol (PEG) are systematically investigated by experiments and molecular simulations. Results demonstrate that ionic dipole interactions introduced by LiTFSI replace hydrogen bonds as the dominant noncovalent force, and the covalent cross‐linked network is verified as the essential prerequisite for mechanical enhancement. The optimized PUUICE exhibits a tensile strength of 65.5 MPa, an ultrahigh fracture elongation of 1227% and high toughness of 268 MJ·m − 3 showing outstanding mechanical strength and ductility. Meanwhile, it possesses reliable temperature and strain sensing performances with favorable sensitivity and stability. This work provides an effective strategy for fabricating high‐performance ICEs and offers a promising candidate for high‐strength flexible sensing materials.