A double network conductive gel with robust mechanical properties based on polymerizable deep eutectic solvent

Abstract

Hydrogels with excellent biocompatibility have become hot topics in the field of flexible electronic wearability. However, high water content and poor mechanical properties limit its application, especially in low temperature environment. We filled the deep eutectic solvent (DES) into the porous structure of polyacrylamide hydrogel (PAAM) by impregnation displacement method. Free radical polymerization was performed in the hydrogel pores using a deep eutectic solvent to form a double-network composite gel with excellent mechanical properties and low temperature resistance. By adjusting the substitution ratio of polyacrylamide hydrogel and deep eutectic solvent, the conductive and mechanical properties of the composite gel were flexibly adjusted. There were a large number of amide and carboxyl functional groups in the composite gel with double network structure, which could form strong hydrogen bond interaction and gave the composite gel excellent mechanical properties (strain up to 1373 %, stress up to 3.14 MPa). In addition, the choline chloride in the deep eutectic solvent provided the gel with good electrical conductivity (∼0.21 ms/cm). Since the water in the composite gel was replaced by a deep eutectic solvent, the gel could resist low temperature (−20 ℃). The large stress-strain gels open up a new way to fabricate organic transparent conductive elastomers for a myriad of future applications in flexible electronics.