Use of a profluorophore for visualization of the rupture of capsules in self-healing coatings

An important category of self-healing materials relies on the release of a healing agent from a capsule upon the occurrence of damage to the material. Visualization of the release of the healing agent is difficult to accomplish. Here we show that a profluorophore can successfully be used to visualize the local release of a healing agent in a self-healing coating. A tetra-functional thiol compound encapsulated in nanocapsules or microcapsules is dispersed in a poly(methyl acrylate) film, in which the profluorophore is molecularly dispersed. A strong fluorescence signal is observed when a cut is introduced in the film. This fluorescence provides clear evidence that the capsules rupture locally during the introduction of a cut. In a more general sense, it proves that profluorophores can be very useful in materials science.