Heteroaggregation between particles modified by polyelectrolyte multilayers

The heteroaggregation of particles is interesting in many fields and particularly in the field of ceramic shaping. In general, heteroaggregation is obtained by mixing powders with opposite surface charges, which may require in some cases surface modifications of the particles. Here we propose to study the behavior of suspensions composed of a mixture of particles with positive and negative charges, created by the adsorption of polyelectrolyte multilayers on their surface. Particular attention is paid to the effect of the number of layers of adsorbed polyelectrolytes and of the ionic strength. This study shows that these surface modifications allow, whatever the number of layers, to have heteroaggregation in the absence of salt. Moreover, depending on the number of adsorbed layers, the addition of salt has a different effect on the suspension behavior. These phenomena can be explained by screening effects already mentioned in the literature for unmixed suspensions of particles modified by polyelectrolyte multilayers. As a consequence, this study highlights that the study of heteroaggregation in these systems is a very simple way to analyze this effect of screening which is difficult to observe on non-mixed suspensions.