Freezing-Induced Mechanoluminescence of Polymer Gels

Mechanochromism can be triggered by different mechanical stimuli, such as tension, compression, shearing, and sonication. Freezing a polymer gel also induces mechanical stress on the polymer network. Herein, freezing-induced mechanoluminescence is demonstrated for the first time by introduction of a tetraarylsuccinonitrile moiety as a light-emitting mechanochromophore at the cross-linking points of a polymer network, in which the mechanical stress induces not only a color change but also light emission. The detailed mechanism and characteristics of this freezing-induced mechanoluminescence were quantitatively evaluated by electron paramagnetic resonance spectroscopy.