Polymer-mediated interaction between a plate and a sphere

A recently developed method is applied to calculate the depletion interacti on between a sphere and a flat plate due to nonadsorbing ideal polymers for arbitrary polymer-sphere ratios. The interaction potential is calculated f rom the polymer concentration profiles surrounding the sphere and plate bas ed on the adsorption around the particles. The polymer concentration profil e in the space near the two particles is the product of the polymer concent ration profile due to the single plate and its profile around the single sp here. The product function profile is in good agreement with profiles calcu lated by computer simulations. The interaction potential derived from the a dsorption using the product function agrees with analytical results for inf initely small and large spheres. It is shown that the force between a flat plate and a sphere goes to a minimum for large polymer-colloid ratios. Thes e results show that a product function applies to the sphere-plate geometry and facilitates the calculation the depiction interaction between colloida l particles in complex cases.