Fluorescence-labeled pyrenesulfonamide response for characterizing polymeric interfaces in composite materials

E-glass fibers were silanized using a 1% (v/v) aqueous solution of gamma-am inopropyltriethoxysilane (APES). Pyrene-sulfonamide conjugates were formed by reaction of 1-pyrenesulfonyl chloride (PSC) in acetonitrile (AcN), with the amine groups immobilized on the glass fiber surface. These pyrene-sulfo namide conjugates were used as fluorescence probes, being a relatively simp le analytical method to study the coating microstructure of polyorganosilox ane layer on glass fibers. The first aim of this work was to estimate possi ble interactions of the polyaminosiloxane coating with surrounding molecule s of different solvents (solvent accessibility to the chromophore). For thi s study, the fluorescence response of pyrene-sulfonamide dye (PSA) was corr elated with solvent polarity parameters. It was concluded that all the stud ied solvents were accessible to the chromophore, and they can gather in two groups, depending on their ability to swell the polioganosiloxane layer. T he second objective was to estimate the rigidity of the coating polymer fro m the temperature dependence of PSA emission. At about 180 K, a sudden chan ge in the behavior of different photophysical parameters of PSA were observ ed. This phenomenon was interpreted as a density change in the polyaminosil oxane attached to the glass fibers.