Interaction potential nonadsorbing polymers

The theory can be extended to include additional interactions. For example, if nonadsorbing polymer is present in solution, exclusion of this polymer from regions where the particles are closer together than the radius of gyration of the polymer molecules produces a potential W. pi that is roughly the osmotic pressure H times the volume of layers from which polymer is depleted. Thus (Patel and Russel 1987 Russel et al. 1989)... 

Practically, the addition of a nonadsorbing polymer to a dispersion can induce flocculation of dispersed particles due to the depletion attraction. This was first observed by Cowell, Lin-In-On, and Vincent [1434]. When large amounts of poly (ethylene oxide) are added to an aqueous dispersion of hydrophilized polystyrene latex particles, the particles start to flocculate. For an organic dispersion, namely, hydrophobized silica particles in cyclohexane, de Hek and Vrij [1435] observed depletion-induced flocculation when dissolved polystyrene was added. Other combinations of particles and polymers followed [1436]. Phase diagrams for different particle-solvent-polymer systems were successfully drawn using the depletion potential of Asakura as interaction potential between dispersed spheres [1437] and for dissolved polymers using statistical mechanics [1438]. 

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