Emulsion Polymerization

Synonyms

Emulsion polymerization and preparation of latexes

Definition

In emulsion polymerization, the monomer, e.g., styrene or methyl methacrylate that is insoluble in the continuous phase, is emulsified using a surfactant that adsorbs at the monomer/water interface. The surfactant micelles in bulk solution solubilize some of the monomer. A water-soluble initiator such as potassium persulfate K₂S₂O₈ is added, and this decomposes in the aqueous phase forming free radicals that interact with the monomers forming oligomeric chains. The most accepted theory of emulsion polymerization is referred to as the coagulative nucleation theory. A two-step coagulative nucleation model has been proposed. In this process, the oligomers grow by propagation, and this is followed by a termination process in the continuous phase. A random coil is produced which is insoluble in the medium, and this produces a precursor oligomer at the θ-point. The precursor particles subsequently grow primarily by...