Super Tough, Highly Ionically Conductive, Self-healing Elastomers with Dynamic Metal Coordination Crosslinks for Flexible Sensors

Abstract

Integrated conductive elastomers with excellent mechanical performance, stable high conductivity, self-healing capabilities, and high transparency are critical for advancing wearable devices. Nevertheless, achieving an optimal balance among these properties remains a significant challenge. Herein, through in situ free-radical copolymerization of 2-[2-(2-methoxyethoxy)ethoxy]ethyl acrylate (TEEA) and vinylimidazole (VI) in the presence of polyethylene glycol (PEG; M_n=400), tough P(TEEA-co-VI)/PEG elastomers with multiple functionalities were prepared, in which P(TEEA-co-VI) was dynamically cross-linked by imidazole-Zn²⁺ metal coordination crosslinks, and physically blended with PEG as polymer electrolyte to form a homogeneous mixture. Notably, Zn²⁺ has a negligible impact on the polymerization process, allowing for the in situ formation of numerous imidazole-Zn²⁺ metal coordination crosslinks, which can effectively dissipate energy upon stretching to largely reinforce the elastomers. The obtained P(TEEA-co-VI)/PEG elastomers exhibited a high toughness of 10.0 MJ·m^-3 with a high tensile strength of 3.3 MPa and a large elongation at break of 645%, along with outstanding self-healing capabilities due to the dynamic coordination crosslinks. Moreover, because of the miscibility of PEG with PTEEA copolymer matrix, and Li⁺ can form weak coordination interactions with the ethoxy (EO) units in PEG and PTEEA, acting as a bridge to integrate PEG into the elastomer network. The resulted P(TEEA-co-VI)/PEG elastomers showed high transparency (92%) and stable high conductivity of 1.09×10^-4 S·cm^-1. In summary, the obtained elastomers exhibited a well-balanced combination of high toughness, high ionic conductivity, excellent self-healing capabilities, and high transparency, making them promising for applications in flexible strain sensors.