Phase behaviour of mixtures of colloidal spheres and excluded volume polymer chains

We study the phase behaviour of mixtures of colloidal spheres and polymers
that have an excluded volume interaction dispersed in a (background) solvent
using the concept of free volume theory. The depletion layer thickness is calculated
from the negative adsorption of polymer segments around a sphere. The
correlation length and thermodynamic properties of the excluded volume interacting
polymer chains in solution are taken into account by using results from
the renormalization group theory. For small polymer-colloid size ratios the difference
with an ideal description of the polymers is small, while for larger size
ratios the gas-liquid coexistence region shifts in the direction of higher polymer
concentrations and at the same time the liquid-crystal coexistence region
becomes more extended. Both the gas-liquid region and the gas-liquid-crystal
region become less extended. These features are compared to experiment.