Shockwave Loading of Mechanochemically Active Polymer Coatings

Thin films of mechanochemically active polymer were subjected to laser-generated, high amplitude acoustic pulses. Stress wave propagation through the film produced large amplitude stresses (>100 MPa) in short time frames (10–20 ns), leading to very high strain rates (ca. 1 × 10⁷ to 1 × 10⁸ s^–1). The polymer system, spiropyran (SP)-linked polystyrene (PS), undergoes a force-induced chemical reaction causing fluorescence and color change. Activation of SP was evident via a fluorescence signal in thin films subject to high strain-rates. In contrast, quasi-static loading of bulk SP-linked PS samples failed to result in SP activation. Mechanoresponsive coatings have potential to indicate deformation under shockwave loading conditions.