Conductive and transparent poly (N-isopropylacrylamide) hydrogels with tunable LCST copolymerized by the green acrylamide-based deep eutectic solvent

Abstract

Smart hydrogels have been widely applied in the bionic intelligent devices for the virtues of biocompatibility, well processibility, environmental sensitivity, and so on. Traditional poly(N-isopropylacrylamide) (PNIPAM) hydrogel has the native response to the temperature change, but the weak strength and narrow phase transition point have limited its applications. Moreover, the poor conductivity of PNIPAM has shields the response signals to the outside. In this work, we have put forward a facile strategy by introducing the ionic conductive deep eutectic solvent (DES) composed of acetylcholine chloride (ACh) and acrylamide (AAm). Followed by one-step copolymerization of AAm and NIPAM, the PAAm-DES/PNIPAM hydrogel formed with the tunable lowest critical solution temperature (LCST), high strength, fine transparence, and good conductivity. As a result, the hydrogel showed the high-sensitive, wide-range and stable response on the outer strain and thermal change, which can play as a sensing element in the intelligent devices. This cost-effective method will be a potential way for fabricating the environmental and multifunctional materials.