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Original scientific paper

Effects of pH and Additives on Aqueous Wetting Films Stabilized by a Triblock Copolymer

O. V. Eliseeva ; Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Wageningen, The Netherlands
N. A. M. Besseling ; Section NanoStructured Materials, Department of Chemical Engineering, Delft University of Technology, Delft, The Netherlands
L. K. Koopal ; Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Wageningen, The Netherlands
M. A. Cohen Stuart ; Laboratory of Physical Chemistry and Colloid Science, Wageningen University, Wageningen, The Netherlands


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Abstract

Effects of pH and additives (NaCl, Na2SO4, NaSCN and urea) on the adsorption of an ABA
triblock copolymer (F127) with polyethylene oxide as the A blocks and polypropylene oxide as
the B blocks, at the interfaces of wetting films, on film drainage and on the interaction forces
in these films are examined using ellipsometry and a thin film balance technique. The influence
of these additives on micellization are studied by static light scattering. The main findings
are that all additives reduce the adsorption at the silica surface and retard the film drainage.
Moreover, high pH values (≈10) destabilize the wetting film if 0.1 mol dm–3 NaCl is present.
The reduction of the adsorbed amount appears to be correlated with a dramatic slow down of
film drainage. The slow drainage as well as the destabilization of the film is attributed to bridging
attraction between a densely covered air-water interface and a very sparsely covered silicawater
interface.

Keywords

aqueous wetting films; disjoining pressure; water-soluble polymers; block copolymer; surfactants; salting-in; salting-out

Hrčak ID:

18666

URI

https://hrcak.srce.hr/18666

Publication date:

30.11.2007.

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