DIRECT MEASUREMENT OF ATTRACTIVE VAN DER WAALS FORCES AND REPULSIVE ELECTROSTATIC FORCES BETWEEN REGENERATED CELLULOSE SURFACES IN AN AQUEOUS ENVIRONMENT

Using the colloidal probe technique, the interaction between carboxymethylated cellulose films and a cellulose sphere was studied. At low pH (pH 3.5), the interaction was dominated by dispersion forces. This was due to the low dissociation of carboxyl groups within the film at pH 3.5. However, at pH greater than 5, the interaction was dominated by an electrostatic repulsion. The increase in pH had the two-fold effect of completely dissociating the charged groups as well as causing appreciable swelling of the film leading to a decrease in the van der Waals component of the interaction. From these results it can be concluded that these cellulose films are suitable for a range of surface forces measurements including electrostatic, van der Waals', steric and adhesion forces. Furthermore, the measurement of forces using the colloidal probe technique can be extended to inorganic particles as well as for interactions between surfaces in the presence of for example wet and dry strength agents and other materials relevant to the paper-making industry.