Abstract
The critical micelle concentration (cmc) of sodium sulfoalkyl alkanoates CnH2n+1COO (CH2) m SO3Na (n=9, 10 and 11; m=2, 3 and 4) in aqueous urea solution have been determined by the spectral change of pinacyanol chloride.
The rate of increase in these cmc values due to the addition of urea increased with the number of carbon atoms inserted between the ester group and the sulfonate group, but decreased with increasing number of carbon atoms in the fatty acid portion of surfactant molecule. Accordingly, among the surfactants containing a given number of carbon atoms in the hydrocarbon chain, the farther the ester group mores from the terminal group to the center of the molecule, the increment in cmc value becomes larger.
