Effect of glycine on the surface activity and micellar properties of N-decanoyl-N-methylglucamide

Surface activity, micelle formation and structure of N-decanoyl-N-methylglucamide in presence of increasing glycine concentrations have been investigated. Changes in the critical micelle concentration of the surfactant with the addition of the amino acid were examined by both surface tension and pyrene 1:3 ratio methods. The observed reduction in the critical micelle concentration was attributed to the structure making action of the additive. Micelle structure parameters were obtained as a function of the glycine concentration by using light scattering and fluorescence-quenching measurements. As regard to the effect of glycine of the micelle size, it was found that both the hydrodynamic radius and the micellar aggregation number increased with the glycine concentration. However, the observed micellar growth seems to be mainly determined by the increase in the aggregation number rather than by changes in the amount of water specifically associated to the micelle. This fact is also supported by the observed trend in the micellar partial specific volume as estimated by complementary density measurements.