Self-assembly, hydration, and structures in N-decanoyl-N-methylglucamide aqueous solutions: effect of salt addition and temperature.

The influence of NaCl addition and temperature on the self-assembly, hydration, and structures of N-decanoyl-N-methylglucamide (MEGA-10) in dilute solution has been investigated by using several experimental techniques, including tensiometry, steady-state fluorescence, density, viscosity, and static and dynamic light scattering. Tensiometry and fluorescence probe studies, by using pyrene as a probe, were used to obtain the critical micelle concentration (cmc) upon the electrolyte addition. The mean micellar aggregation numbers (N(agg)) as a function of the salt addition were obtained by both static light scattering and static quenching methods. The N(agg) values estimated by both methods were found to be in good agreement. It was found that the increase in the micelle size, produced by the addition of NaCl, is due to the increase in the aggregation number and in the amount of water non-specifically associated to the micelle. On the other hand, we have observed that the aggregation number remains invariant in the temperature range studied, whereas the hydrodynamic radius slightly decreases. The effect of electrolyte addition and temperature on the properties of MEGA-10 micelles is much less pronounced than those observed in the traditionally used POE-based surfactants.