Mechanism of Emulsification of Styrene Using Hexadecyltrimethylammonium Bromide-Cetyl Alcohol Mixtures

  • Y. J. Chou
  • M. S. El-Aasser
  • J. W. Vanderhoff


Ionic emulsifier-cetyl alcohol mixtures give more stable emul sions than the ionic emulsifiers alone, e. g., the emulsification of styrene using hexadecyltrimethylammonium bromide-cetyl alcohol mixtures gives better stability during emulsion polymerization than ammonium bromide alone. The emulsification of this system was investigated by the conductometric titration of the aqueous mixed emulsifier system at 63° with styrene. At the hexadecyltrimethylammonium bromide-cetyl alcohol ratios which gave good stability, the conductance decreased with increasing styrene concentration to a minimum, then increased to a maximum and decreased slightly or leveled off. During the initial decrease, the sample was translucent and comprised a small number of relatively large (ca. 500nm) droplets which broke down to form a large number of very small (ca. 130nm) droplets; beyond the first inflection point, the sample gradually became opaque and the very small droplets coalesced to form a constant number of larger (ca. 200nm) droplets; beyond the second inflection point, the sample was opaque and the constant number of particles grew in size and narrowed in distribution to form monodisperse (ca. 350nm) droplets. The initial mixed emulsifier system contained crystalline rod-like particles (1–2μm length; 0.1–0.2μm diameter), which disappeared as the relatively large droplets broke down to form very small droplets. With hexadecyltrimethylammonium bromide alone, the conductance decreased to an inflection point, then decreased more slowly thereafter; the sample was translucent before the inflection point and opaque afterwards; no crystalline rod-like particles were observed. These results suggest that the hexadecyltrimethylammonium bromide and cetyl alcohol form a crystalline complex which disappears as the emulsion droplets are formed, to release hexadecyltrimethylammonium bromide to the aqueous phase, and then reappears on the droplet surfaces as an adsorbed complex of the optimum ratio.


Droplet Size Inflection Point Osmium Tetroxide Emulsion Polymerization Polyvinyl Acetate 
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Copyright information

© Plenum Press, New York 1980

Authors and Affiliations

  • Y. J. Chou
    • 1
  • M. S. El-Aasser
    • 1
  • J. W. Vanderhoff
    • 1
  1. 1.Emulsion Polymers InstituteLehigh UniversityBethlehemUSA

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