The properties of a buried epoxy/glass interfacial region were studied by c
ovalently grafting a fluorescent probe to the glass surface. A (dimethylami
no)nitrostilbene (DMANS) fluorophore was tethered to a triethoxysilane coup
ling agent, generating a fluorescently labeled silane coupling agent (FLSCA
). The glass surface was coated with a silane layer that was doped with sma
ll amounts of FLSCA. The emission maximum from grafted FLSCA was different
than when the dye was dissolved in bulk resin, suggesting a different inter
facial structure. When the dye was dissolved in bulk cured resin, a red shi
ft in the emission maximum was detected as the resin temperature was increa
sed. A distinct break in the fluorescence maximum vs temperature slope was
detected at the glass transition of the bulk resin. The slope became larger
at temperatures above T-g. A similar break was observed from grafted FLSCA
, suggesting that the grafted dye was sensitive to an apparent glass transi
tion in the buried interfacial region. The temperature of the apparent inte
rfacial transition measured by grafted FLSCA could be lower or higher than
the bulk polymer T-g, depending on the initial structure of the grafted sil
ane layer.