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Phasediagrams of Polymer-Colloid-Mixtures

Colloid-Polymer mixtures show new phenomena in their phase behavior. In a pure colloidal system one finds a  fluid-crystal coexistence region of the hard sphere system (Fig. 1 yellow region).




  Fig. 1 Phase diagram of a pure colloidal solution

This phase diagram corresponds to the phase diagram of a polymer-colloid mixture with cpolymer=0. The key parameter which determines the topology of the phase diagram is the ratio  x (x = rg/a  , a= radius of the colloidal particle, rg= radius of gyration of the polymer).



For small x the addition of non-adsorbing polymer just expands the colloidal fluid-crystal coexistence region of the hard sphere system (Fig. 2 left). For larger x a 3 phase coexistence of colloidal gas, fluid and crystal phases is observed ( Fig. 2 right). The crossover between these phase-diagrams is found at  x = 0,25.

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