Mechanochemical Regulation of a Photochemical Reaction

We introduce the concept of mechanochemically
gated photoswitching.
Mechanical regulation of a photochemical reaction is exemplified using
a newly designed mechanophore based on a cyclopentadiene–maleimide
Diels–Alder adduct. Ultrasound-induced mechanical activation
of the photochemically inert mechanophore in polymers generates a
diarylethene photoswitch via a retro-[4 + 2] cycloaddition reaction
that photoisomerizes between colorless and colored states upon exposure
to UV and visible light. Control experiments demonstrate the thermal
stability of the cyclopentadiene–maleimide adduct and confirm
the mechanical origin of the “unlocked” photochromic
reactivity. This technology holds promise for applications such as
lithography and stress-sensing, enabling the mechanical history of
polymeric materials to be recorded and read on-demand.