Hybrid polymer latexes

Hybrid polymer latexes will be defined here as colloidal dispersions in which at least two distinct polymers exist within each particle. The two polymers may form a homogenous blend within the particle or microphase separation may occur. There are two general routes for their preparation. The first involves the use of a mini-emulsion polymerization process, in which a first polymer, most often prepared via polycondensation (or polyaddition), is dissolved in an unsaturated monomer (or a mixture of monomers). The solution is first emulsified into small droplets under a high shear process and then polymerized through a radical polymerization process. A variation of this route involves the synthesis of the polycondensate directly in the mini-emulsion. The second route involves a seeded emulsion polymerization of unsaturated monomer(s), in which the polycondensate is modified for use as a seed in the emulsion polymerization. Most often, styrenic and acrylic monomers are used, while the polycondensate may be alkyd resins, polyesters, epoxy resins, polyurethanes, or other polymers. The two routes are described in detail, as are the properties of the resulting materials (mostly as films). Up to now, there have been very few trials for the comparison of the two main routes. Most often the comparison is related to blends of the two kinds of emulsified polymers. (C) 2007 Elsevier Ltd. All rights reserved.