Oxidization and Salting Out Synergistically Induced Highly Elastic, Conductive, and Sensitive Polyvinyl Alcohol Hydrogels

Abstract

Although a variety of functional polyvinyl alcohol hydrogels (PVAHG) with attractive mechanical and electrochemical properties have been fabricated using traditional freeze-thaw cycling, this approach is usually relatively complicated, time-consuming and relies essentially on the use of PVA chains with a weight-average molecular weight above 60000. Here a new strategy capable of assembling relatively low-molecular-weight (≈30000) polyvinyl alcohol (PVA) into highly crosslinked physical hydrogels is developed. By exploiting ammonium persulfate as a simple and versatile oxidant to simultaneously provide oxidizing and salting-out effects to the polymeric building blocks, PVAHG with excellent and tailorable elasticity, conductivity and sensitivity can be achieved building on the strong intermolecular hydrogen bonding between the newly formed ─COOH and ─CHO terminations and the inclusion of abundant inorganic ions. The hydrogels cannot only act as effective wearable wireless sensors for detecting output resistance signals but also be further employed to construct a motion-mapped self-propelled robotic arm that is able to instantly and accurately map the motion of human bodies. This study may provide new insights into polymer chemistry, hydrogel sensing, and soft robotics.