Analytical phase diagram for colloid-polymer mixtures

We present a theoretical analysis of the phase behavior of colloid-polymer mixtures which applies to all polymer/colloid size ratios q. It accounts for the crossover from a constant length scale R (radius of gyration) in the colloid limit (small q) to the concentration-dependent correlation length xi in the protein limit (q>1). We obtain predictions that fully agree with observations and simulations. In the protein limit the colloid concentrations eta along the binodals become independent of q and the polymer concentrations phi scale as q(1/gamma), where gamma=0.77 is the scaling exponent in xi similar to phi(-gamma): phase diagrams plotted as phi q(-1/gamma) vs eta are then independent of q. The liquid window in the protein limit is narrow.