TEMPERATURE-DEPENDENT FORCES BETWEEN HYDROPHILIC MICA SURFACES COATED WITH ETHYL(HYDROXYETHYL)CELLULOSE

The forces acting between hydrophilic mica surfaces across aqueous ethyl(hydroxyethyl)cellulose (EHEC) solutions have been investigated with the surface force technique. It was found that the adsorbed amount is rather low at these surfaces and that the adsorbed polymer molecules are easily squeezed out from the gap between the surfaces on compression at low temperatures (20-degrees-C). The force-distance curve is purely repulsive at this temperature, and up to the point where the EHEC molecules are squeezed out, all forces were found to be reversible on compression/decompression. The adsorbed amount increases somewhat with temperature, but remains quite low at all temperatures. Moreover, it becomes increasingly difficult to squeeze out the adsorbed polymer molecules by applying an external force. It was found that the temperature dependence was not completely reversible over the incubation time used (20 h). On diluting the solution to roughly 10(-4) wt %, only a limited desorption occurs. The temperature dependence of the interaction after dilution is similar to that before dilution. A comparison of the forces acting between EHEC-coated mica surfaces and EHEC-coated hydrophobic surfaces demonstrates the importance of the surface-polymer interaction.