Fracture-induced mechanochemical activation is achieved for the first time in a structural engineering
polymer. Rubber toughened PMMA is lightly cross-linked (1.0 mol%) with the mechanophore spiropyran
by free radical polymerization. Single Edge Notch Tension tests are performed on the spiropyran-linked
material and a distinct change in color and fluorescence is detected at the crack tip, indicating the
mechanochemical transformation of the spiropyran molecules. The degree of mechanophore activation is
quantified via fluorescence imaging and is observed to increase with increasing crack length. The region
of mechanophore activation correlates directly with the size of the plastic zone ahead of the crack tip.