Conductive and Tough Smart Poly(N-isopropylacrylamide) Hydrogels Hybridized by Green Deep Eutectic Solvent

Conductive smart hydrogels with several virtues such as similar characters to biological tissues, sensitive response to ambient variations, have shown their excellent talents in the field of flexible electrical sensors, biomedical devices and directional transportation. However, complex preparing approaches or the instable inner structures have not only been time-consuming, but also broken up the performance and reliability of the smart hydrogel-based devices. In this work, a facile one-step method is put forward to synthesize a kind of conductive poly(N-isopropylacrylamide) (PNIPAM) hydrogel doped by a new green solvent of deep eutectic solvent (DES) containing choline chloride (ChCl) and acrylic acid (AA). Through the copolymerization of AA and NIPAM, the mechanical strength of the DES-doped PNIPAM hydrogels is drastically improved compared to the pure PNIPAM gels, and some doped hydrogels lost the typical phase transition temperature of PNIPAM. Moreover, due to the ionic property of DES, the hybrid hydrogels also present the thermal-depending conductivity as well as sensitive deformation response, which can be used as a smart switch in a circuit or a sensing element with environmental response ability. The cost-effective preparation and the attractive performance of the DES-doped hydrogels offer a new avenue to construct multi-functional materials.

Automated summary

A cost-effective and facile method to synthesize a conductive poly(N-isopropylacrylamide) hydrogel doped with deep eutectic solvent (DES) is proposed in this study, demonstrating enhanced mechanical strength and thermal-dependent conductivity. The hybrid hydrogels show potential applications in flexible electronic sensors and environmental response elements.