Visualizing separation at composite interfaces via spirolactam mechanophores†

Abstract

The failure of interfaces between polymers and inorganic substrates often leads to deteriorated performance, as is the case for polymer matrix composites. Interfacial mechanophores (iMPs) have the potential to fluorescently measure interfacial failures. Spirolactam-based mechanophores are of interest due to their readily available synthetic precursors and compatibility with epoxy matrices. In this work, spirolactam is covalently bound at the interface of silica surfaces and epoxy, chosen due to the industrial relevance of glass fiber composites. The iMPs are mechanically activated through uniaxial tension applied to the composite while the resulting fluorescent response is observed in situ with a confocal microscope. Due to their real time sensing capabilities, iMPs are a promising technique to measure interfacial failures in composite materials more easily than with traditional optical microscopy techniques.