Shock and Rarefaction Wave Induced Activation in Mechanophores

Mechanophores are a novel class of material in which mechanical activation leads to a premeditated reaction within the polymer that leads to an alteration of some property. Numerous experimental and theoretical studies have explored and characterized mechanoluminescence, mechanocatalytic, and mechanochromic responses under strain loading. However, mechanical loading in condensed matter, especially shock compression, results in more complex, many-body (MB) deformations. Mounting theoretical work has shown that these MB deformations can result in complex accelerations and alterations to chemical reactions. Here, we perform shock compression in a PMMA + Spiropyran system and analyze how isomerization reactions occur during both compression and high strain release due to rarefaction waves and spall. We find that, for strong shocks, both compression and expansion waves can induce significant activation on the timescale of the loading. The many-body deformations of the loaded mechanophores are assessed to evaluate the mechanochemical influence on activation.