Antifreezing and Highly Elastic Hydrogels Based on Hydrogen-Bond Regulation and Hydrophobic Crosslinking for Multifunctional Flexible Devices.

Conventional hydrogels tend to freeze at low temperatures and exhibit significant mechanical hysteresis during cyclic deformation, which impairs their cycling stability and substantially restricts their applications in flexible devices employed in extremely cold environments. Herein, a synergistic strategy combining hydrophobic crosslinking and hydrogen-bond regulation is proposed to achieve antifreezing and highly elastic hydrogels. The hydrogels are one-step prepared by polymerization of acrylamide in zinc triflate solutions using hydrophobic 1,9-bis(acryloyloxy)nonane as a crosslinker. The hydrophobic crosslinker endows the hydrogel with an ultrahigh stretchability of 2266% and a toughness of 0.51 MJ m-3, while Zn(OTf)2 regulates the hydrogen-bonding interactions to reduce mechanical hysteresis and depress the freezing point. The as-prepared hydrogels show a hysteresis ratio of 6.61% during cyclic deformations and maintain mechanical flexibility even at ultralow temperatures of -70 °C. Owing to the antifreezing and highly elastic features, the resultant hydrogels demonstrate robust functionalities as electrolytes for zinc-ion pouch batteries and strain/temperature sensors at ultralow temperatures. This study provides an effective route to achieve high stretchability, low hysteresis, and superior antifreezing performance in one hydrogel for flexible energy storage and wearable sensing materials under extreme cold conditions.