LETTER TO THE EDITOR Wall tensions of model colloid–polymer mixtures

Using the Asakura–Oosawa–Vrij model for mixtures of hard sphere colloids and non-adsorbing polymer coils, an analytic formula for the interfacial free energy of the fluid mixture in contact with a hard wall is obtained within a scaled-particle treatment. The results compare well with explicit density functional calculations for the binary mixture. We also give expressions for the wall tension of the mixture when polymers interact via a simple stepfunction pair potential, and for the case of contact with a polymer-coated wall, which we take to be hard for the colloids but penetrable for the polymers. On the gas side of the fluid–fluid demixing binodal we confirm the wetting transition at the hard wall and predict complete drying of the polymer-coated wall on the liquid side of the binodal. Mixtures of sterically-stabilized colloidal particles and non-adsorbing globular polymers suspended in an organic solvent are valuable soft matter systems to study demixing phase transitions and wetting phenomena at walls; for a recent review see [1]. Controlling th