Amphiphilic properties of synthetic glycolipids based on amide linkages, 3. Temperature and concentration dependence of the reduced viscosity of gel‐forming alkyl gluconamides

Abstract

Abstract In order to follow the process of aggregation, viscosity measurements in dilute aqueous solution were performed with two carbohydrate amphiphiles: (i) N ‐octylgluconamide (C 8 ‐GA) and (ii) N ‐decanoyl‐ N ‐methylglucamide (C 10 ‐MGA). Both compounds ten to form a gel on cooling, the former at 65°C, the latter at 10°C. Electron micrographs have shown that the gels are composed of a loose network of thin, regularly twisted helical ropes. By viscosity measurements over a wide range of temperatures and concentrations, typical changes of the reduced viscosity were observed. Results are discussed with respect to the critical micelle concentration (CMC), the Krafft point, i. e. the critical temperature of crystallization ( T c ), and the cloud point ( T cp ). It is concluded that micellar aggregation to rod‐shaped particles, quasi‐crystalline aggregation to highly hydrated gels, and crystallization of monomers, the latter mediated by hydrogen bonding, are involved and compete with each other.