Mechanochemical changes in absorption or fluorescence in solid polymers are important for the development of new methods of damage sensing, and must be demonstrated in structural polymers such as epoxies for widespread use. With this in mind, we have observed that diamine-cured epoxies containing 4,4′-diaminodiphenyl methane (DDM) framework display mechanochemical changes in both absorption and fluorescence. Samples change from original “blue” to mechanochemically activated “red” fluorescence in response to uniaxial compressive deformation beginning in the early stages of strain hardening. Accompanying the “red” fluorescence is an increase in radical concentration; both are impermanent in time, suggesting the reactive intermediate as the fluorophore. Orange and green chromophores are generated by compression as well; the orange chromophore is the red-emitting fluorophore while the green chromophore is non-fluorescent at ambient conditions. Our work indicates that the DDM structure is the origin of the mechanochromic responses, and stoichiometric variation and degree of cure are strong determinants for whether orange or green chromophores will form. Based on these results the red-emitting orange chromophore is proposed as a reactive radical intermediate of core DDM structure, generated by bond scission reactions on the epoxy network. The green chromophore is a quinoidal methine resulting from the intermediates.

固体聚合物中吸收或荧光的机械化学变化对于开发新的损伤检测方法非常重要，必须在结构聚合物（例如环氧树脂）中得到广泛证明。考虑到这一点，我们已经观察到含有4,4'-二氨基二苯甲烷（DDM）骨架的二胺固化环氧树脂在吸收和荧光方面均表现出机械化学变化。响应于应变硬化早期开始的单轴压缩变形，样品从原始的“蓝色”荧光变为机械化学活化的“红色”荧光。伴随“红色”荧光的是自由基浓度的增加；两者都不是及时的，提示反应性中间体为荧光团。橙色和绿色生色团也通过压缩产生。橙色发色团是发红光的荧光团，绿色发色团在环境条件下不发荧光。我们的工作表明，DDM结构是机械变色反应的起源，化学计量的变化和固化程度是决定橙色或绿色生色团的重要决定因素。基于这些结果，提出了红色发光的橙色发色团，作为核DDM结构的反应性自由基中间体，是通过环氧基网络上的键断裂反应生成的。绿色生色团是由中间体产生的喹啉次甲基。化学计量变化和固化程度是决定橙色或绿色生色团的重要决定因素。基于这些结果，提出了红色发光的橙色发色团，作为核DDM结构的反应性自由基中间体，是通过环氧基网络上的键断裂反应生成的。绿色生色团是由中间体产生的喹啉次甲基。化学计量变化和固化程度是决定橙色或绿色生色团的重要决定因素。基于这些结果，提出了红色发光的橙色发色团，作为核DDM结构的反应性自由基中间体，是通过环氧基网络上的键断裂反应生成的。绿色生色团是由中间体产生的喹啉次甲基。