Gelation and phase separation in colloid-polymer mixtures

We discuss theoretically the phase diagram of a solution containing both linear polymers in a good solvent and small colloidal particles. We consider the case where the colloidal particles are very small and where the polymer adsorbs at the surface of the particles. The partition functions of the various complexes between polymers and colloidal particles are calculated using a scaling approach. In a dilute solution, star-like polymers with a particle at the core are formed if the particle density is very low and necklaces of particles on one polymer are formed if the particle density is large. In a semi-dilute solution, we find a gelation due to the cross-linking of the polymer by the particles and a phase separation.