Abstract
The effects of solubilizates on the fading behavior of 4-phenylazo-1-naphthol (4-OH) in aqueous solutions of anionic-nonionic mixed surfactant systems are described; the systems studied are sodium dodecyl sulfate (SDS) — octadecyl poly(oxyethylene) ethers (C18POE20). The fading rate of 4-OH in the mixed solution was independent of the addition of octane. By adding octanoic acid, the rate became faster. On the other hand, the 1-octanol slowed the rate. The fading speed of 4-OH decreased as the concentration of the alcohol and the number of carbon atoms in the alcohol molecule, used as a solubilizate, increased. The sizes of mixed micelles penetrated by the solubilizate were dependent on the kind of oily materials and on the alkyl chain lengths in the molecules of normal higher alcohols. Relative viscosities and effective specific volumes in the mixed micellar solutions increased with the increase in the concentration of 1-octanol and octanoic acid, and with increasing the number of alkyl groups in the alcohol molecule. The effect of solubilizates on the fading behavior of 4-OH was found to be dependent on the differences in their solubilization sites in mixed micelles. A solubilizate with a strong polar group supported a hydrophilic-hydrophilic interaction, whereas one including a weak polar group did not.
Published Version
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