Ultrahigh ionic conductivity and alkaline tolerance of poly (amidoxime)-based hydrogel for high performance piezoresistive sensor

The preparation of polymer hydrogels with excellent mechanical stability and high conductivity still remains huge challenges in practical applications as wearable electronics and energy storage. Herein a new strategy is proposed to prepare uniform poly(amidoxime)/polyethyleneimine (PAO/PEI) hydrogel through hydrogen bond interactions. The as-prepared PAO/PEI hydrogels demonstrate good compressive strength (7.07 kPa) and transparency. Due to the excellent ionic adsorption properties of PAO containing the amidoxime groups, it is firstly found that the PAO/PEI hydrogels show a ultrahigh ionic conductivity of 19.1 S m-1 in 6 M LiCl, and the hydrogels also present an excellent alkaline tolerance with ionic conductivity as high as 22.35 S m- 1 in 6 M KOH. Furthermore, graphene oxide (GO) is introduced into the PAO/PEI system to form PAO/PEI/reduced GO (rGO) hydrogels which exhibit higher mechanical strength, and can endow electronic conductivity. Moreover, both the as-prepared PAO/PEI/LiCl1 (1 M LiCl) and PAO/PEI/rGO/LiCl1 (1 M LiCl) hydrogels as pressure sensors, present high sensitivity (5.09 and 8.55 kPa-1 respectively), ultra-low detection limit (20 Pa), and excellent cycle stability (1000 compression cycles). It can be expected that the PAO-based hydrogels with high ionic conductivity developed firstly will have a broad application prospects in wearable sensing devices and energy storage/con-version devices.