Strengthening of Hydrophobic Bonding and the Increase in the Micellar Degree of Ionization in Cetyltrimethylammonium Bromide Aqueous Solutions by Amphiphiles and the Micelle-Water Distribution Coefficient

  • Mohammad Abu-Hamdiyyah
  • Christiane M. El-Danab


We have investigated the effect of amphiphilic additives on the critical micelle concentration (CMC) and the micellar degree of ionization in cetyltrimethylammonium bromide (CTAB) and obtained a linear relationship between the logarithm of the relative lowering of the CMC with additive concentration and logarithm of the corresponding relative increase in the micellar degree of ionization. Using this empirical relation with the recently found equation relating the effect of the additive on the CMC and on the micellar degree of ionization with the distribution coefficient of the additive between the aggregates and the surrounding aqueous solution (K) we obtain the relation
$$ {{ - dln{x_f}} \over {d{y_f}}}\, = \,\theta K $$
with θ a constant approximately independent of the additive equal to 0-8 ±0.1, and xf and yf are the free mole fraction concentrations of the surfactant and of the additive in the aqueous solution respectively. Using this value of θ we have calculated the values of K for alkanols from their effect on the CMC of CTAB and found them to be in reasonable agreement with the experimental values obtained by Miyashita and Hayano.


Critical Micelle Concentration Distribution Coefficient Sodium Lauryl Sulfate Propylene Carbonate Propylene Oxide 
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Copyright information

© Plenum Press, New York 1986

Authors and Affiliations

  • Mohammad Abu-Hamdiyyah
    • 1
  • Christiane M. El-Danab
    • 1
  1. 1.Department of ChemistryUniversity of KuwaitKuwaitKuwait

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