| Abstract: | To ensure the stability of the concentrated emulsions that are employed as precursors for polymerization, a two-step concentrated emulsion polymerization pathway is described. In the first step, the monomer is partially polymerized by heating at 50°C until a certain conversion is reached. Subsequently, the partially polymerized monomer is used as the dispersed phase to prepare a concentrated emulsion in which water constitutes the continuous phase. The concentrated emulsion has a large volume fraction of the dispersed phase (0.74–0.99) and the appearance of a gel. Several typical monomers are employed to correlate the stability of the concentrated emulsion and the extent of partial polymerization of the dispersed phase. It was found that monomers, which cannot lead to stable concentrated emulsions, can generate them after partial polymerization. Subsequent polymerization of the concentrated emulsion leads to latex particles. Copolymers and polymer composites were also prepared by the two-step procedure. In the latter case, water was replaced with a solution of a hydrophilic monomer in water as the continuous phase. © 1992 John Wiley & Sons, Inc. |
