用和频发生(SFG)振动光谱学方法探测紫外光和等离子体表面改性聚二甲基硅氧烷的动力学过程研究
In numerous applications in microfluidics, cell growth, soft lithography, and molecular imprinting, the surface ofpoly(dimethylsiloxane) (PDMS) is modified from a hydrophobic methyl-terminated surface to a hydrophilic hydroxylterminatedsurface. In this study, we investigated molecular structural and orientational changes at the PDMS-airinterface in response to three commonly used surface modification processes: exposure to long-wavelength ultravioletlight (UV), exposure to short-wavelength UV that generates ozone (UVO), and exposure to oxygen plasma (OP). Thesurfaces of two PDMS compositions (10:1 and 4:1 of base polymer/curing agent) were probed during modification,using monolayer-sensitive IR + visible sum frequency generation (SFG) vibrational spectroscopy, with two differentpolarization combinations. During PDMS surface modification, the peak intensities of CH3 side groups and CH2cross-link groups decreased, while peak intensities of Si-OH groups increased. There was no significant change inthe average orientation of the CH3 groups on the PDMS surface during modification. The concentration of CH3 groupson the surface decreased exponentially with time, for all three UV, UVO, and OP modification processes, with firstorder kinetics and time constants of approximately 160, 66, and 0.3 min, respectively. At steady state, residual CH3groups were detected at the PDMS surface for UV and UVO treatments however, there were negligible CH3 groupsdetected after OP modification.