Organization of amphiphiles, part XII: studies on the interaction of glycine with aqueous micelles of polyoxyethylated nonyl phenols

Abstract

The effect of glycine on micellization of polyoxyethylated nonyl phenols of varying oxyethylene units (15 and 20) has been investigated by surface tension, fluorescence, DLS, zeta potential and UV-Visible spectral measurements. The critical micellar concentration (CMC) is seen to decrease with an increase of glycine concentration from both surface tension and fluorescence data. The CMC value obtained from fluorescence measurement is coincident with the data obtained from surface tension as well as zeta potential measurements. The surface excess concentration (Γmax), the minimum area per molecule (Amin), and the surface pressure at the CMC (πCMC) have been estimated from surface tension data. Thermodynamic parameters of adsorption and micellization have been evaluated and discussed. The changes in aggregation number and hydrodynamic radius (from DLS data) on addition of glycine suggest an increase in size of the micelle. Suitable model of interaction of glycine with the nonionic surfactants has been suggested.