Mechanoluminescent Imaging of Osmotic Stress-Induced Damage in a Glassy Polymer Network

A chemiluminescent mechanophore, bis(adamanty1-1,2-dioxetane), is used to investigate the covalent bond scission resulting from the sorption of chloroform by glassy poly(methyl methacrylate) (PMMA) networks. Bis(adamantyl)-1,2-dioxetane units incorporated as cross-linkers underwent mechanoluminescent scission, demonstrating that solvent ingress caused covalent bond scission. At higher cross-linking densities, the light emission took the form of hundreds of discrete bursts, widely varying in intensity, with each burst composed of 10(7)-10(9) photons. Camera imaging indicated a relatively slow propagation of bursts through the material and permitted analysis of the spatial correlation between the discrete bond breaking events. The implications of these observations for the mechanism of sorption and fracture are discussed.