Mechanochemical Activation of Covalent Bonds in Polymers with Full and Repeatable Macroscopic Shape Recovery.

Covalent mechanochemistry within bulk polymers typically occurs with irreversible deformation of the parent material. Here we show that embedding mechanophores into an elastomeric poly(dimethylsiloxane) (PDMS) network allows for covalent bond activation under macroscopically reversible deformations. Using the colorimetric mechanophore spiropyran, we show that bond activation can be repeated over multiple cycles of tensile elongation with full shape recovery. Further, localized compression can be used to pattern strain-induced chemistry. The platform enables the reversibility of a secondary strain-induced color change to be characterized. We also observe mechanical acceleration of a flex-activated retro-Diels-Alder reaction, allowing a chemical signal to be released in response to a fully reversible deformation.