Immobilizing a fluorescent dye offers potential to investigate the glass/resin interface

Silane coupling agents are commonly applied to glass fibers to promote fibe r/resin adhesion and enhance durability in composite parts. In this study, a coupling agent multilayer on glass was doped with trace levels of the dim ethylaminonitrostilbene (DMANS) fluorophore. The fluorophore was immobilize d on the glass surface by tethering the molecule to a triethoxy silane coup ling agent, creating the DMANS/silane coupling agent molecule (DMSCA). DMSC A was then diluted with commonly used coupling agents and grafted to a glas s microscope coverslip to create a model composite interface. A 53-nm blue shift in fluorescence from the immobilized DMSCA can be followed during cur e of an epoxy resin overlayer, giving this technique potential to monitor t he properties of the fiber/resin interface during composite processing. Con tact angle measurements on these coupling agent layers were similar in the presence or absence of the DMSCA molecule, suggesting that trace levels of the fluorescent probe did not affect the structure of the layer. The immobi lized DMSCA molecule behaved similarly to the DMANS precursor in solution. Both showed longer wavelength fluorescence in more polar environments. (C) 2000 Academic Press.