Effect of UV-ozone treatment on poly(dimethylsiloxane) membranes: surface characterization and gas separation performance.
A thin SiO(x) selective surface layer was formed on a series of cross-linked poly(dimethylsiloxane) (PDMS) membranes by exposure to ultraviolet light at room temperature in the presence of ozone. The conversion of the cross-linked polysiloxane to SiO(x) was monitored by attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), energy-dispersive X-ray (EDX) microanalysis, contact angle analysis, and atomic force microscopy (AFM). The conversion of the cross-linked polysiloxane to SiO(x) increased with UV-ozone exposure time and cross-linking agent content, and the surface possesses highest conversion. The formation of a SiO(x) layer increased surface roughness, but it decreased water contact angle. Gas permeation measurements on the UV-ozone exposure PDMS membranes documented interesting gas separation properties: the O(2) permeability of the cross-linked PDMS membrane before UV-ozone exposure was 777 barrer, and the O(2)/N(2) selectivity was 1.9; after UV-ozone exposure, the permeability decreased to 127 barrer while the selectivity increased to 5.4. The free volume depth profile of the SiO(x) layer was investigated by novel slow positron beam. The results show that free volume size increased with the depth, yet the degree of siloxane conversion to SiO(x) does not affect the amount of free volume.
Fu
Ywu-Jang
YJ
Department of Biotechnology, Vanung University, Chung-Li 32061, Taiwan.
Qui
Hsuan-zhi
HZ
Liao
Kuo-Sung
KS
Lue
Shingjiang Jessie
SJ
Hu
Chien-Chieh
CC
Lee
Kueir-Rarn
KR
Lai
Juin-Yih
JY
D004129:Dimethylpolysiloxanes; D005740:Gases; D008567:Membranes, Artificial; D018625:Microscopy, Atomic Force; D010126:Ozone / Q000737:chemistry*; D017550:Spectroscopy, Fourier Transform Infrared; D013499:Surface Properties; D014466:Ultraviolet Rays
D004129:Dimethylpolysiloxanes; D005740:Gases; D008567:Membranes, Artificial; C013830:baysilon; D010126:Ozone