Optical Force Monitoring in Polymeric Materials with a Coumarin‐Based Mechanophore

Optical mechanophores offer a powerful platform for the real‐time, nondestructive detection of mechanically induced damage in polymers. However, the exploitation of mechanophores for fundamental investigations of deformation processes and the prediction of failure in technologically critical applications has been constrained by their responsivity to other stimuli, laborious synthesis, and limited control of their photophysical and mechanical properties. Here, we report a cyclobutane‐based mechanophore that activates a fluorescent coumarin dye through the application of mechanical stress in solution and in the solid state. We demonstrate the preparation of the mechanophore in two synthetic steps, its incorporation into linear and crosslinked polymers, and its thermal and photochemical stability, establishing the basis for a new class of mechanophores with tunable spectral and mechanical characteristics.