Nanoscale Characterization of Epoxy Interface on Silica

The objective of this study is to carry out nanoscale characterization of the epoxy resin interface on silica by determining the glass-transition temperature (T-g) and molecular conformation at the interface by means of a novel nondestructive method. The T-g was determined by fluorescence lifetime measurements using evanescent wave excitation. It was revealed that the T-g of epoxy resin at a distance of 30 nm from the interface was 10 K higher than that at a distance of 80 nm. The chemical composition and molecular conformation were analysed by X-ray photoelectron spectroscopy and sum-frequency generation (SFG) spectroscopy, respectively. The SFG data revealed that unreacted epoxy group remained at the interface. The T-g of epoxy resin increased in the regions near the interface, and the epoxy group remained unreacted at a distance of ca. 10 nm or less from the interface.