ATTRACTIVE POTENTIAL BETWEEN CONFINED COLLOIDS AT LOW IONIC-STRENGTH

Digital video microscopy is used to locate the positions of 1.27 mum d iameter polystyrene spheres suspended in low ionic strength water and confined between two glass plates. A method is developed to obtain the pair potential of the colloidal particles from measurements of the pa ir-correlation function of both dilute and moderately concentrated dis persions. We find that the measured pair potential has an attractive c omponent much greater than predicted by the Derjaguin-Landau-Verwey-Ov erbeek theory of nonconfined colloids and suggest that the confining p lates are responsible for the observed deviations from theory.