Interactions of cellulose surfaces: Effect of electrolyte

The forces between spherical particles of cellulose (20-30 mu m) have been measured in different solutions using an atomic force microscope, with a view to understanding the interactions in a model papermaking system. At low ionic strength (0.1 mM KBr), the interaction profile is dominated by a long range double layer force and shorter ranged electrosteric force. A qualititatively similar profile is observed at high pH, but in this case both the double layer force and electrosteric force increase as a consequence of cellulose charging. Conversely, the two force contributions both decrease in the presence of calcium ions. At high ionic strength (10 mM KBr) the electrosteric force is absent and the forces appear to be due solely to double layer forces. Overall, the results show that the surface is composed of looser chains that extend out into the solution, the conformation of which is highly sensitive to the solution conditions.