Microemulsion polymerization of styrene stabilized by sodium dodecyl sulfate and short-chain alcohols

Styrene microemulsion polymerizations with different short-chain alcohols [ n-CiH2i+1OH (CiOH), where i = 4, 5, or 6] as the cosurfactant were investig ated. Sodium dodecyl sulfate and sodium persulfate (SPS) were used as the s urfactant and initiator, respectively. The desorption of free radicals out of latex particles played an important role in the polymerization kinetics. An Arrhenius expression for the radical desorption rate coefficient was ob tained from the polymerizations at temperatures of 50-70 degreesC. The poly merization kinetics were not very sensitive to the alkyl chain length of al cohols compared with the temperature effect. The maximal polymerization rat e in decreasing order was C6OH > C4OH > C5OH. This was related to the diffe rences in the water solubility of CiOH and the structure of the oil-water i nterface. The feasibility of using a water-insoluble dye to study the parti cle nucleation mechanisms was also evaluated. The parameters chosen for the study of the particle nucleation mechanisms include the cosurfactant type (CiOH), the SPS concentration, and the initiator type (oil-soluble 2,2 ' -a zobisisobutyronitrile versus water-soluble SPS). (C) 2001 John Wiley & Sons , Inc.