Simple statistical thermodynamic model of the heteroaggregation and gelation of dispersions and emulsions

The heteroaggregation behaviour of mixtures of equal-sized particles (type A + type B) exhibiting short-ranged attractive interactions is investigated using the sticky hard-sphere model. The average cluster size is calculated as a function of the total particle volume fraction, the binary mixture composition, and the A-B stickiness interaction parameter tau(-1)(AB). We show that a value of tau(-1)(AB) = 10(2), equivalent to an attractive well depth of similar to 5kT in a realistic continuous pair potential, leads to a state of heteroaggregation just below the gelation threshold of the equimolar mixture of volume fraction 0.1. We discuss the conditions under which the assumptions of this statistical thermodynamic model are satisfied experimentally, with particular reference to recent data on the heteroaggregation behaviour of protein-stabilized emulsions and latex particle dispersions. (C) 2011 Elsevier Inc. All rights reserved.