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 (approximate to 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.
|Journal||Croatica Chemica Acta|
|Publication status||Published - 2007|