In recent years there has been a growing interest in modifying surface properties of inorganic oxides, polymer films and other solid substrates with tethered polymers. Applications of such surfaces include, colloid stabilization, adhesion promotion or reduction, wetting, lubrication, biocompatibility, size exclusion chromatography, and reducing fouling of ultrafiltration membranes. In all of the above applications, information regarding surface hydrophilicity (or water wettability) is essential to assessing surface behavior and thus the expected surface performance in the above applications.
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In the present research, surface wettability and hydrophilicity of
terminally-grafted PVP and PVAc on smooth silicon wafers is being studied
by advancing and receding contact angle measurements. Polymer graft yield
and surface roughness are assessed by thermogravimetric analysis (TGA) and
atomic force microscopy (AFM), respectively.
Research results have shown that surface wetting trends correlate with polymer graft yield and grafted chain length and density. In contrast, lack of correlation between surface roughness and contact angle hysteresis suggests that nanometer-scale surface roughness does not contribute to the observed hysteresis.
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Our work has suggested that reorientation of surface-grafted polymer chains could account for changes in surface wettability, similar to those observed for solid polymer films. Contact angle analysis, based on the theory of van Oss and co-workers, demonstrated that the degree of hydrophilicity of polymer-grafted smooth inorganic surfaces depends on both polymer functionality and polymer graft yield.
Current studies are continuing to evaluate surface wettability over a wide range of grafted polymer surface densities. The ultimate goal is to establish predictive models and correlations to a priori predict the expected surface wetting of tethered polymer surface. Such information would be particularly useful for applications in tribology, membrane filtration, and in vivo biomedical devices.
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References:
Ron S. Faibish, Wayne Yoshida and Yoram Cohen, "Contact Angle Study of Polymer-Grafted Silicon Wafers", J. Colloid and Interface Science, in press.
Surface Charge and Adsorption
| Grafted polymers can be utilized to mask surface hydroxyls on inorganic oxide surfaces. Therefore, interaction of certain solutes with surface hydroxyls can be significantly reduced. |
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| Adsorption can also be reduced by steric effects when the surface is obstructed from the solute |
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See Publications for additional information.
Last update:
01/04/2004
