J. Stellbrink, J. Allgaier, and D. Richter, J. Dzubiella¹, A. Jusufi¹, C.N. Likos¹, C. von Ferber¹, and H. Löwen¹, A.B. Schofield², P.A. Smith², W.C.K. Poon², and P.N. Pusey^2
1Theoretical Physics II, Heinrich-Heine-Universität Düsseldorf, Germany
²Department of Physics and Astronomy, The University of Edingburgh, United Kingdom

We examine the phase diagrams of star polymer-colloid mixtures for star arm nurobers f = 2, 6,16,32 and different star-colloid size ratios q. In all samples with q ~ 0.49, addition of polymer to suspensions with volume fraction nc ~ 0.1- 0.4 brought about, successively, phase separation into colloidal gas and liquid (or demixing), triple coexistence of gas, liquid and crystal, and gas-crystal coexistence. In samples with q ~ 0.18, addition of polymer first led to fluid-crystal coexistence; a metastable gas-liquid binodal buried inside the equilibrium fluid-crystal coexistence region was encountered at higher polymer concentrations. Theoretically, we solve the thermodynamically selfconsistent Rogers- Young integral equations for binary mixtures using three effective pair potentials obtained from direct molecular computer simulations. The numerical results show a spinodal instability. The demixing binodals are approximately calculated, and found to be consistent with experimental observations.