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 vi ew 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 qualiti tatively similar profile is observed at high pH, but in this case both the double layer force and electrosteric force increase as a consequence of cel lulose charging. Conversely, the two force contributions both decrease in t he presence of calcium ions. At high ionic strength (10 mM KBr) the electro steric force is absent and the forces appear to be due solely to double lay er forces. Overall, the results show that the surface is composed of looser chains that extend out into the solution, the conformation of which is hig hly sensitive to the solution conditions.