Observation of wall wettability under imposed flow by fluorescence depolarization: dependence on surface oxygen content and degree of polymer branching
- 作者：Quintella ; Cristina M. ; Musse ; Ana Paula S. ; Castro ; Martha T.P.O. ; Gonç ; alves ; Cristiane C. ; et. al.
- 关键词：Fluid microdynamics ; Intermolecular forces ; PLF ; Dynamic interactions ; Adhesion ; Drag
- 刊名：Journal of Colloid and Interface Science
- 出版年：2005
- 期刊代码：125_00219797
- 类别：ch
- 出版时间：January 1, 2005
- 卷：281
- 期：1
- 页码：201-208
- 文件大小：363 K
摘要
This work was concerned with the dependence of the interfacial tension ( Formula Not Shown ) on surface degree of oxygen content and on polymer branching degree. The static Formula Not Shown was evaluated by contact angle ( Formula Not Shown ) and the dynamic Formula Not Shown by fluorescence depolarization of molecular probes seeded in induced flows of monoethylene glycol. The latter results were interpreted using statistical covariant analysis. Two different systems of flowing films were studied: free films flowing on the surfaces on which they impinge and films flowing inside 1-mm-thick microflow cells. The solid surfaces were polyethylene of low density, medium density, high density, and linear with low density, polypropylene, vinyl acetate co-polymer with oxygen content of 15%and 28%, borosilicate, and tin dioxide. Increase in oxygen content of the surface decreased both the static and the dynamic Formula Not Shown, which demonstrated that the presence of oxygen atoms hindered wetting. Only the dynamical Formula Not Shown was sensitive to polymer branching, and it increased as branching degree decreased. This was attributed to the higher hydrogen-atom density at the surface, which favored temporary intermolecular bonds between the surface and the flowing liquid.