Electric Field Actuation of Tough Electroactive Hydrogels Cross-Linked by Functional Triblock Copolymer Micelles

Abstract

Multiresponsive polyelectrolyte hydrogels with extraordinary toughness have great potential in soft device applications. Previously we have demonstrated a series of tough and multiresponsive hydrogels by using multifunctional triblock copolymer (Pluronic F127 diacrylate, F127DA) micelles to cross-link cationic polyelectrolyte chains into 3D network. Herein, we further synthesize negatively charged hydrogels comprising 2-acrylamido-2-methyl propylsulfonic acid (AMPS) monomers by using F127DA micelles as cross-linkers. Similar to the positive nanomicelle (NM) hydrogels, the negative NM hydrogels exhibited a compressive strength up to 59 MPa with a fracture strain up to 98%, and tensile fracture strain higher than 2000%. These charged hydrogels were actuated by electric field when immersed in salt solutions. The effects of electrolyte concentration, electric field strength, and ionic monomer content on the electric actuation behavior of these electroactive hydrogels (EAHs) have been systematically investigated. It is concluded that the electroactive hydrogels show a fast actuation rate with a bending angle up to 87° at 120 s and the bending angle was cyclically reversed upon changing bias direction without a large decrease. This study demonstrates that such tough and multiresponsive electroactive hydrogels may have great potential in sensors, actuators, switches, and artificial muscles.

Keywords: electric-field; electroactive; hydrogels; micelles; tough.