Mechanically activated fluorescence in polymer matrix composites

Polymer matrix composites (PMCs) offer design solutions to produce composites for numbers of critical applications. Nanoparticle additives like carbon nanotubes and quantum dots have been investigated for their ability to improve the conductivity, thermal stability, and mechanical strength of traditional composites. Current mechanoresponsive polymers rely on the use of the breakage of covalent bonds to induce self-healing reactions or changes in optical properties. Their active response is mediated by a functional polymer backbone, which limits the polymeric materials available. Thus, we propose to tune the interactions between fluorescent quantum dots, fluorescently labeled carbon nanotubes, and novel matrix chemistries to probe composite failure mechanisms. We find that pronounced changes in fluorescence emerge following plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the fluorescence occurs in response to mechanical activation. We anticipate that force activation of fluorescence for quenching pairs can serve as a general strategy for the development of new PMCs building blocks that impart polymeric materials with desirable functionalities ranging from damage sensing to enhancements in mechanical strength