Abstract
Mechanophores are molecules that undergo productive, covalent chemical transformations
in response to mechanical force. Over the last decade, a variety of mechanochromic
mechanophores have been developed that enable the direct visualization of stress in
polymers and polymeric materials through changes in color and chemiluminescence. The
recent introduction of mechanochemically gated photoswitching extends the repertoire
of polymer mechanochromism by decoupling the mechanical activation from the visible
response, enabling the mechanical history of polymers to be recorded and read on-demand
using light. Here, we discuss advances in mechanochromic mechanophores and present
our design of a cyclopentadiene–maleimide Diels–Alder adduct that undergoes a force-induced
retro-[4+2] cycloaddition reaction to reveal a latent diarylethene photoswitch. Following
mechanical activation, UV light converts the colorless diarylethene molecule into
the colored isomer via a 6π-electrocyclic ring-closing reaction. Mechanically gated
photoswitching expands on the fruitful developments in mechanochromic polymers and
provides a promising platform for further innovation in materials applications including
stress sensing, patterning, and information storage.
1 Introduction to Polymer Mechanochemistry
2 Mechanochromic Reactions for Stress Sensing
3 Regiochemical Effects on Mechanophore Activation
4 Mechanochemically Gated Photoswitching
5 Conclusions
Key words
polymer mechanochemistry - mechanophore - diarylethene - photoswitch - mechanochromism
- Diels–Alder reaction
