Star-polymers as depleting agents of colloidal hard spheres

We examine the phase behavior of star-polymer colloid mixtures for star-to-colloid size ratios smaller than unity, by employing recently derived effective interactions between the constituent particles. Tuning the arm number of the star-polymers provides a natural bridge between the well-known borderline models of colloid-polymer and binary hard-sphere mixtures. By canonically tracing out the star-polymers, we derive accurate effective depletion potentials between the colloids and examine the stability of the demixing transition with respect to the crystallization of the colloids. We find that the former is metastable with respect to freezing for arm numbers f greater than or similar to 10 at all size ratios.