Effective interactions between star polymers and colloidal particles

Using monomer-resolved molecular dynamics simulations and theoretical argum ents based on the radial dependence of the osmotic pressure in the interior of a star, we systematically investigate the effective interactions betwee n hard, colloidal particles and star polymers in a good solvent. The releva nt parameters are the size ratio q between the stars and the colloids, as w ell as the number of polymeric arms f (functionality) attached to the commo n centre of the star. By covering a wide range of q's ranging from zero (st ar against a flat wall) up to about 0.75, we establish analytical forms for the star-colloid interaction which are in excellent agreement with simulat ion results. A modified expression for the star-star interaction for low fu nctionalities, f less than or similar to 10 is also introduced.