Effects of photo-excitation and organic vapor treatment on vapor sorption behavior of sputtered fluoropolymer films

Investigation of sorption capacities for volatile organic compounds of radi o-frequency-sputtered fluoropolymer films has revealed that they are affect ed by the applied voltage and by supplemental photo-excitation using ultrav iolet light irradiation during sputtering. The photoassisted effects of pro ducing unsaturated carbons on the sputtered tetrafluoroethylene film are re vealed by infrared, electron spin resonance, and X-ray photoelectron spectr oscopies. Measurements of sorption capacities and computational chemical ca lculation for six-membered cyclic hydrocarbons revealed that the pi-charact er of the solute molecule is a decisive molecular descriptor for sorption b ehavior of the sputtered fluoropolymers. The pi-character of the sputtered fluoropolymer films can be enhanced by a photo-assisted effect, which can a lso increase the affinities for pi-characterized solutes by pi-pi interacti on. This is further clarified by the fact that the photo-assisted fluoropol ymer film has a larger sorption capacity for highly pi-conjugated double ar omatic ring systems (C10H8): naphthalene than for slightly pi-conjugated, b ut polar, isomer: azulene. It was also found that saturated organic vapor ( p-xylene and 2-butanone) sorption can enhance the sorption capacities of th e sputtered fluoropolymer by restructuring induced by solvation and radical reaction. (C) 1999 Elsevier Science S.A. All rights reserved.