Controlled aggregation of polymer lattices and encapsulation of hydrophobic substances in polymer clusters

The major objective of this work was to determine the influence of different parameters, such as temperature, hydrodynamic conditions, and amount and nature of cationic surfactant used to destabilize the latex, on the properties of the polymer clusters obtained through the aggregation of submicron latices.; The $z$ potential of the particles obtained through emulsion polymerization was satisfactory explained using a simplified model which relates the characteristic of the polymer (chemical nature of the end groups, number average molecular weight) and the colloidal properties of the latex (particle size, $z$ potential). Based on this model, an insight on the surface chemistry of these latices can be obtained, i.e. a spatial location of the charged end groups.; The trends observed in the aggregation of these latices were explained through calculations of the fundamental forces involved in this process. While for some of these forces precise calculations were possible (Van der Waals attraction, electrostatic repulsion, hydrodynamic break up force), for others, only semi-quantitative calculations (steric interactions) or only a qualitative assessment of their presence (hydrophobic and hydrophilic interactions) were possible.; Based on the experimental evidence obtained, a three-step mechanism for the aggregation process was proposed. This mechanism involves the formation of a three-dimensional network with a gel-like structure, formation of small, compact aggregates (termed primary aggregates) through the mechanical disrupture of this network, and further aggregation of the primary aggregates into larger structures, termed secondary aggregates.; By doing a comparative study of the aggregation process in different colloidal systems, we were able to demonstrate the role played by latex surface mobility in controlling the average size of the aggregates. This force is due to the chain mobility which occurs at temperatures close to the glass transition temperature of the polymer.; Narrow size distributions, with GSDs between 1.2–1.35 were obtained only for the latices containing acrylic acid. It was shown that on the surface of these particles there is a hairy layer formed by the polyacrylic acid chains. The thickness of this layer is dependent on the chemical environment and temperature. Attempts to construct adsorbed steric layers that can improve the aggregation behavior of the PS latices were unsuccessful until now. The destruction of the original steric layer from the particles containing copolymers of acrylic acid leads to a change in the characteristics of the aggregates (larger GSDs).; It was experimentally proven that a controlled release device can be obtained through the aggregation of polymer latices. A controlled amount of a hydrophobic substance can be encapsulated and delivered up to a volume of effluent which is several thousand times the volume of the aggregates (or, in time, between hours and a few days, depending on the contact time). The release profile can be changed in the desired way by varying the size of the aggregates and their internal structure. (Abstract shortened by UMI.)...