The field of polymer mechanochemistry investigates the use of mechanical force to promote selective chemical transformations. Polymer chains transduce external mechanical forces to a particular covalent bond in mechanically sensitive molecules called mechanophores, resulting in a specific chemical reaction. We report on a new mechanophore based on a cyclopentadiene−maleimide Diels−Alder adduct that undergoes a retro-[4+2] cycloaddition reaction promoted by mechanical force to reveal a diarylethene (DAE) photoswitch. Initially, the mechanophore is photochemically inert because it does not possess the necessary 6π electronic framework required for electocyclization; however, ultrasound-induced mechanical activation of the mechanophore covalently linked to polymer chains generates a DAE photoswitch, which isomerizes between colorless and colored forms upon exposure to UV and visible light. Control experiments confirm the mechanical origin of the revealed photochromic activity and illustrate the thermal stability and reversible switching properties of the cyclopentadiene-based DAE photoswitch.

Photoswitch generation using mechanical force

2019 Fall National Meeting

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