Mechanochromic response of pyrene functionalized nanocomposite hydrogels

Mechanochromic polymers display detectable changes in their fluorescence emission upon deformation of their macromolecular structure. Here, we study reversible mechanochromism of pyrene functionalized nanocomposite hydrogels. Highly stretchable nanocomposite hydrogels are prepared by free radical polymerization of poly(N-isopropylacrylamide) and pyrene terminated poly(ethylene) glycol methacrylate copolymers in the presence of nanoclay, acting as the physical crosslinker. Mechanochromic behavior is characterized through uniaxial tensile experiments, where force, deformation, and fluorescence emission are simultaneously measured. To demonstrate the application of mechanochromic nanocomposite hydrogels in pressure sensing, membranes are used to detect differential pressures on the order of 10² Pa. We envision the integration of these mechanochromic hydrogels in the design of novel force and pressure sensors with application to mechanics, fluid dynamics, and biophysics.