Surface Modification of Sylgard-184 Poly (dimethyl siloxane) Networks by Ultraviolet and Ultraviolet/Ozone Treatment
K Efimenko, William E. Wallace, Jan Genzer
We report on studies probing the effect of ultraviolet (UV) radiation and ultraviolet/ozone treatment (UVO), on the modification of poly(dimethyl siloxane) (PDMS) networks. The effect of the UV light wavelength and ambient conditions on the surface properties of PDMS is studied using a palette of experimental probes, including static contact angle, Fourier transform infrared spectroscopy in the attenuated total reflection geometry, near-edge X-ray absorption fine structure, and X-ray reflectivity. Our results show that when exposed to UV, PDMS undergoes chain scission, involving both main backbone and the side-groups. The radicals formed during this process recombine forming a network whose wetting properties are close to those of a pure PDMS. In contrast to the UV radiation, the UVO treatment causes very significant changes in the surface and subsurface structure of PDMS. Specifically, the molecular oxygen and ozone created during the UVO process interact with the UV-modified PDMS. The extent to which the PDMS gets modified depends on the amount of the molecular oxygen/ozone created during the UVO process. As a result of these interactions the sub-surface region of PDMS is modified in that the PDMS-UVO surface contains a large number of hydrophilic groups (e.g., ?OH). In addition, the material density within the first 5 nm of PDMS, thus the region that was most modified with UVO, reaches about 50% of that of silica. Our data shows that denser PDMS networks are more susceptible to the UVO induced modification.
, Wallace, W.
and Genzer, J.
Surface Modification of Sylgard-184 Poly (dimethyl siloxane) Networks by Ultraviolet and Ultraviolet/Ozone Treatment, Journal of Colloid and Interface Science, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=851912
(Accessed February 27, 2024)