Tough, mechanoresponsive hydrogels have broad and significant impacts on fundamental research and practical applications, but have proved to extremely challenging. The poor solubility of mechanophores makes them difficult to be integrated into a highly hydrophilic network of hydrogels. Here, a newly developed polyacrylamide-co-methyl acrylate/spiropyran (poly(AM-co-MA/SP)) hydrogel, crosslinked by SP mechanophore in the presence of surfactant TWEEEN80 micelles, demonstrates its multi-stimuli responsive and mechanically strong properties. The optimal hydrogels can achieve thermo-, photo-, and mechano-induced color changes with excellent mechanical properties (tensile stress=1.45 MPa, tensile strain=6, elastic modulus=1.1 MPa, fracture energy=7300 J/m2, tearing energy=3200 J/m2). Due to the presence of dynamically reversible SP crosslinkers and micellar structures, the hydrogels exhibited reversible changes both in color and mechanical properties between the force-, heat-, and UV light-induced deformation state and the white light-induced recovery state. More impressively, we further design a conceptual hydrogel strain sensor to monitor color change under the stretching and relaxing processes. This work offers a new strategy to incorporate hydrophobic SP mechanophores into hydrophilic network for fabricating tough and mechanoresponsive hydrogels, which would be highly useful in wearable soft sensors and devices with programmable and versatile properties.

Highly tough, mechanoresponsive, and self-recovery hydrogels used as strain-induced color sensors

2019 Spring National Meeting

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