Vapor Phase Fluorination of Silica Surface with Chlorofluoromethanes and CF4

For a surface modification, fluorinations of silica samples including a quartz fiber and a commercial glass fiber, were carried out at around 500 °C in a conventional flow reactor. The surface compositions before and after the fluorination were determined by XPS analyses. Among chlorofluoromethanes and CF4, CCl3F was the most effective for fluorination. Surface OH groups were completely removed or replaced by the fluorination. Adsorptions of water vapor, hexane, hexafluoropropene, and octafluorocyclobutane showed that the silica surface became more hydro- and lipophobic after the fluorination. On the contrary, the chlorofluoro-methanetreated surface exhibited a higher affinity to the perfluorocarbons compared to the untreated surface.