Star-polymers as depleting agents of colloidal hard spheres

PACS. 61.20.-p – Structure of liquids. Abstract. – 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 be-tween 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 re-spect to the crystallization of the colloids. We find that the former is metastable with respect to freezing for arm numbers f 10 at all size ratios. Introduction. – Typical soft-matter systems are always found in solution and in the form of multicomponent mixtures. Two of the most common models of this type, that have received a lot of attention recently, are mixtures of hard spheres (colloids) and free, nonadsorbing chains on the one hand, and the binary hard-sphere mixture (BHS) of two species with a variable size ratio on the other. The theoretical investigations of the colloid-polymer (CP) mixtur