INTERACTIONS BETWEEN MICA SURFACES IN THE PRESENCE OF CARBOHYDRATES

The forces acting between muscovite mica surfaces across solutions containing either uncharged carbohydrates (cyclodextrin and sucrose) or a weakly charged hemicellulose (xylan) were measured using a surface force apparatus, Both the uncharged carbohydrates and xylan adsorb onto the mica basal plane, The adsorption of the uncharged carbohydrates results in a decrease in the long-range electrostatic double-layer force, thereby indicating a reduction in surface charge density. At a low ionic strength (1 x 10(-3) M KBr) the adsorption of xylan is very limited, and the resulting adsorbed layer has a thickness similar to that observed for cyclodextrin and sucrose, When the ionic strength of the solution is increased, a stow buildup of the adsorbed xylan layer takes place. The functional form of the interactions between these thicker layers is consistent with the forces expected for anchored polymer brushes in a good solvent. (C) 1995 Academic Press, Inc.