SILANIZATION OF RADIO-FREQUENCY GLOW-DISCHARGE MODIFIED EXPANDED POLY(TETRAFLUOROETHYLENE) USING (AMINOPROPYL)TRIETHOXYSILANE

Previous work from this laboratory has shown the ability to incorporate hydroxyl-containing functionality onto fluoropolymer surfaces. Specifically, expanded poly(tetrafluoroethylene) (ePTFE) and poly(vinylidene fluoride) were surface modified via H2/H2O and H2/MeOH radio frequency glow discharge plasma treatments. In order to confirm the presence of reactive -OH, this present study describes the successful covalent linkage of (aminopropyl)triethoxysilane to the modified ePTFE surfaces. This attachment is effected through the observed formation of silanol bonds between the modified ePTFE membrane and the product poly[(aminopropyl)siloxane]. The interfacial bonding and structure and then determined by electron spectroscopy for chemical analysis, attenuated total reflectance Fourier transform infrared spectroscopy, and scanning electron microscopy. Finally, the concentration of -OH reactive sites on the modified ePTFE membrane is quantified through reactions of fluoroscein isothiocyanate (FITC) to amine groups of the bonded APS. FITC-a fluorescent molecule-is reversibly and selectively removed from the amine bonding site and then quantified through fluorescent spectroscopic techniques. The FITC concentration then provides a measure of surface reactive -OH concentration on the modified ePTFE membranes.