Zwitterionic dual-network strategy for highly stretchable and transparent ionic conductor

Abstract

The development of flexible electronic devices depends on the research of stretchable conductive materials. In this work, we report a green and transparent ionic conductor with high stretchability based on green deep eutectic solvents (DESs) and biocompatible zwitterionic polymer. The dual-network (DN) strategy was achieved by two-step UV-initiated polymerization, and the DN ion gels consisting of the physically cross-linked zwitterionic poly(3-dimethyl(methacryloyloxyethyl) ammonium propane sulfonate) (PDMAPS) and chemically cross-linked poly(2-hydroxyethyl methacrylate) (PHEMA) were prepared, using choline chloride/ethylene glycol (ChCl/EG) DESs as solvents. The prepared DN ion gels present outstanding tensile properties (breaking strain over 1000%), high transparency (>90%), good room temperature ionic conductivity (0.315 S m−1), and good fatigue resistance. In addition, due to the ultra-low volatility and low freezing point of the ChCl/EG DESs, the DN ion gel shows high stability and frost resistance (−60 °C). Finally, the performance of the DN ionic gel-based flexible strain sensor is investigated to evaluate its application potential in wearable flexible electronic devices. The DN ion gel strain sensor can sensitively and stably monitor human motions. The outstanding characteristics such as non-toxicity and biocompatibility of both the conductive filler and polymer matrix for preparing the DN ion gels in this work provide a new view for the development of green flexible conductive devices with high performance and multiple functions.