SOLUBILIZATION OF PENTANOL BY MICELLES OF CATIONIC SURFACTANTS AND BINARY-MIXTURES OF CATIONIC SURFACTANTS IN AQUEOUS-SOLUTION

The solubilization of pentanol in aqueous solutions of individual cationic surfactants and binary mixtures of cationic surfactants at 20-degrees-C has been investigated using head-space chromatography. Complete solubilization isotherms have been determined for pentanol in micelles of the surfactants hexadecylpyridinium chloride (CPC), trimethyltetradecylammonium chloride (C14Cl), benzyldimethyltetradecylammonium chloride (C14BzCl), benzyldimethylhexadecylammonium chloride (C16BzCl), and hexadecyltrimethylammonium bromide (C16Cl). In every case, a large decrease in the solubilization equilibrium (or partition) constant occurs on increasing the mole fraction of pentanol in the micelles (X); a factor of 3-5 reduction in the equilibrium constant occurs as X increases from nearly zero to nearly 0.9. Solubilization results have also been determined for mixed micelles of Cl4Cl and Cl4BzCl (system I) and CPC and C16BzCl (system II). Large positive synergistic effects reported previously for system I and large antisynergistic effects for system II are not confirmed by the results of the present studies. For both of these mixed micellar systems, small decreases in the value of the solubilization equilibrium constant, relative to values predicted with an assumed additivity relationship, are observed.