THERMODYNAMICS OF AQUEOUS CARBOHYDRATE SURFACTANT SOLUTIONS

The paper deals with the application of the micelle formation theory, developed by Nagarajan and Ruckenstein [R. Nagarajan, E. Ruckenstein, Langmuir 7 (1991) 2934-2969] and Nagarajan [R. Nagarajan, in: K. Esumi (Ed.), Structure-Performance Relationships in Surfactants, Dekker, Ne w York, 1997, pp. 1-81; R. Nagarajan, Adv. Colloid Interface Sci. 26 ( 1986) 205-264] to various n-alkyl-beta-D-glucopyranoside surfactants, differing in the surfactant tail length (n-octyl-beta-D-glucopyranosid e C(8)G(1), n-decyl-beta-D-glucopyranoside C(10)G(1) and dodecyl-beta- D-glucopyranoside C(12)G(1)). The model predicts that the carbohydrate surfactant molecules assemble for energetic reasons in spherical bila yer vesicles. The critical micellar concentration as function of the t emperature shows a minimum value. The formed micellar aggregates exhib it a broad distribution of sizes. It is demonstrated in this study tha t the thermodynamic theory in combination with phase separation thermo dynamics can be used successfully to described the phase separation, w hich occurs for the system C(10)G(1) + water and C(12)G(1) + water at low surfactant concentrations. (C) 1998 Elsevier Science B.V. All righ ts reserved.