Dispersion Polymerization

Definition

Dispersion polymerization is usually applied for the preparation of nonaqueous latex dispersions, and hence, it is referred to as NAD. The method has also been adapted to prepare aqueous latex dispersions by using an alcohol-water mixture. In the NAD process, the monomer, normally an acrylic, is dissolved in a nonaqueous solvent, normally an aliphatic hydrocarbon and an oil-soluble initiator, and a stabilizer (to protect the resulting particles from flocculation, sometimes referred to as “protective colloid”) is added to the reaction mixture. The most successful stabilizers used in NAD are block and graft copolymers. These block and graft copolymers are assembled in a variety of ways to provide the molecule with an “anchor chain” and a stabilizing chain. The anchor chain should be sufficiently insoluble in the medium and has a strong affinity to the polymer particles produced. In contrast, the stabilizing chain should be soluble in the medium and strongly solvated by its...