Surface functionalization of polymeric substrates from radio frequency-plasma-generated silylium ions

The mechanism of rf-discharge-induced fragmentation of SiCl4 was studied by separating the components of the molecular mixture (GC-MS, HR-MS) resulting from the ex situ recombination of plasma-generated active species and by simulating the plasma-induced chemistry under low-energy electron mass spectroscopy conditions. It was found that SiCl3+ (silylium) ions and corresponding radicals were the predominant molecular fragments in the discharge; accompanied by small quantities of SiCl2- and SiCl-based species. Plasma origin SiClx active species were effectively implanted onto polypropylene, polyester, cellulose, and polytetrafluoroethylene surfaces and the modified relative surface atomic compositions were evaluated by photoelectron spectroscopy. Analytical data indicate that SiClx fragments can effectively replace H, OH, and even fluorine atoms on the polymeric structures. Surface characteristics like wettability and morphology of the plasma modified polymeric substrates were estimated by dynamic contact angle evaluation and atomic force microscopy. It was demonstrated that the surface modifications are reproducible and stable with time. Potential applications of SiCl4 plasma modified polymeric surfaces are suggested. (C) 1996 American Vacuum Society.