Preserved elastic modulus and enhanced adhesion in long-term and thermally stable glycol gels via affine shrinkage upon water evaporation

Abstract

Glycol-based polymer gels have emerged as stable alternatives to water-based hydrogels, offering intrinsic advantages owing to the ultra-low volatility and high thermal stability of glycol solvents. However, progress has been limited by persistent challenges in simultaneously achieving both long-term mechanical reliability and strong interfacial adhesion under ambient and extreme conditions. Here, we report a strategy to overcome these limitations by selectively evaporating water from poly(2-hydroxyethyl acrylate) gels prepared in water–glycol co-solvent systems. This controlled drying induces predominantly affine shrinkage, preserving the polymer network's elastic modulus while substantially increasing elongation at break and minimizing mechanical hysteresis during cyclic loading. Moreover, evaporation-driven enrichment of hydroxyl groups at the gel surface yields a more than sixfold increase in interfacial adhesion strength. As a result, the optimized glycol gels maintain robust mechanical performance and strong adhesion across an exceptionally broad temperature range (−20 °C to 120 °C). In contrast, conventional hydrogels collapse and lose adhesion at these extreme temperatures. These findings establish a practical design paradigm for thermally stable polymer gels, thereby paving the way for long-term biomedical adhesives and wearable electronics.