Concepts for manipulating macroscopic properties of colloids through the formation of polymer depletion gels

Polymers are often added to colloidal dispersions to modify their rheological and tactile properties. This is a difficult approach because the addition of an even small amount of polymer can profoundly affect the macroscopic properties of the dispersions. It has long been known that adding non-absorbing polymer to dispersions can result in large interparticle depletion potentials that result in particle aggregation and phase separation. However, over the last few years it has also been realized that very large depletion potentials can result in gelation. This paper provides the basic concepts to outline the effect, show how these ideas transfer to complex vesicle mixtures, and the relationship to the macroscopic properties of the depletion gels.