M. Ouyang et al., UV-ozone induced growth of a SiOx surface layer on a cross-linked polysiloxane film: characterization and gas separation properties, J MEMBR SCI, 177(1-2), 2000, pp. 177-187
A thin SiOx surface layer was formed on porous Nylon(R) membranes coated wi
th a cross-linked polysiloxane by exposure to ultraviolet light at room tem
perature in the presence of atmospheric oxygen. The transformation of the c
ross-linked polysiloxane to SiOx was monitored by X-ray photoelectron spect
roscopy (XPS), attenuated total reflectance infrared spectroscopy (ATR-IR),
contact angle analysis and atomic force microscopy (AFM). A continuous sur
face layer of SiOx formed after about 1 h of UV exposure. AFM analysis reve
aled that a nodular structure with a characteristic size less than 0.5 nm f
ormed after extended UV exposure. Gas permeation measurements on the compos
ite membranes documented interesting gas separation properties: the CO2 per
meance of the cross-linked polysiloxane/Nylon(R) composite membrane before
irradiation was 8.9x10(-8) mol m(-2) s(-1) Pa-1, and the CO2/N-2 selectivit
y was 22; after UV-ozone induced formation of the SiOx surface layer, the p
ermeance decreased to 5.1x10(-8) mol m(-2) s(-1) Pa-1 while the selectivity
for CO2/N-2 increased to 48. (C) 2000 Published by Elsevier Science B.V.