Highly conductive and tough double-network hydrogels for smart electronics

Development and understanding of highly mechanically robust and electronically conducting hydrogels are extremely important for ever-increasing energy-based applications.Conventional mixing/blending of conductive additives with hydrophilic polymer network prevents both high mechanical strength and electronic conductivity to be presented in polymer hydrogels.Here,we proposed a double-network(DN)engineering strategy to fabricate PVA/PPy DN hydrogels,consisting of a conductive PPy-PA network via in-situ ultrafast gelation and a tough PVA network via a subsequent freezing/thawing process.The resultant PVA/PPy hydrogels exhibited superior mechanical and electrochemical properties,including electrical conductivity of~6.8 S/m,mechanical strength of~0.39 MPa,and elastic moduli of~0.1 MPa.Upon further transformation of PVA/PPy hydrogels into supercapacitors,they demonstrated a high capacitance of~280.7 F/g and a cycle life of 2000 galvanostatic charge/discharge cycles with over 94.3%capacity retention at the current density of 2 mA/cm2 and even subzero temperatures of−20℃.Such enhanced mechanical performance and electronic conductivity of hydrogels are mainly stemmed from a synergistic combination of continuous electrically conductive PPy-PA network and the two interpenetrating DN structure.This in-situ gelation strategy is applicable to the integration of ionic-/electrical-conductive materials into DN hydrogels for smart-soft electronics,beyond the most commonly used PEDOT:PSS-based hydrogels.