Ultrasonic Relaxation and Carbon-13 NMR Studies of Dialkylammonium Chloride Micelles

Article abstract of DOI:10.1021/j100395a031

Ther cmc values of several dialkylmethyl and dialkyldimethylammonium chloride surfactants, with a number of carbon atoms per alkyl chain, n_c, between 6 and 12, have been measured by conductivity and ultrasonic absorption techniques.The results agree with earlier cmc measurements for dialkyldimethylammonium chlorides with n_c equal to 8, 10, and 12.The aggregation number of dihexylmethylammonium chloride has been determined by 13C NMR.The value of 6 has been found, which is in good agreement with the values obtained for monoalkyl chain surfactants.The kinetic study of the fast exchange process occurring in micellar solutions has been carried out by means of ultrasonic absorption methods on aqueous solutions of dialkylmethylammonium chlorides with 6, 7, and 8 carbon atoms in each alkyl chain.The relaxation time τ₁ which characterizes this fast process increases as the alkyl chain length increases as for monoalkyl surfactants.The τ₁ values are much closer to those found for straight-chain surfactants with 6, 7, and 8 carbon atoms than those found for straight-chain surfactants with 12, 14, and 16 carbon atoms.The kinetic results are discussed in terms of Aniansson and Wall's theory.