Self-healable gradient copolymers
Self-healing materials typically suffer from poor mechanical performance in terms of practical applications. Herein, a self-healable copolymer with a gradient distribution of hard segments on ionic polymer chains is designed. By the optimization of the monomer sequences and physical cross-linking, the copolymer exhibits excellent mechanical properties with Young's modulus up to 286 MPa and toughness over 33 MJ m−3, which represents a significant improvement compared with traditional self-healing materials. Imidazolium in this copolymer not only generates strong dynamic ionic associations and imparts mending ability, but also provides ionic conductivity for potential device applications. Environment-insensitive self-healing in the presence of moisture, water and artificial sweat is achieved. Strain sensors with rapid response (<114 ms) and high durability (no performance decrease after 7000 cycles of tensile test) are fabricated using the gradient copolymers, opening an avenue for high-performance wearable devices using polymeric materials.