Abstract
A sugar-based gemini surfactant N,N’-dialkyl-N,N’-dilactobionamideethylenediamine (2CnLac, where n represents alkyl chain lengths of 8, 10, 12, and 14) was synthesized by reacting N,N’-dialkylethylenediamine with lactobionic acid. The adsorption properties of 2CnLac were characterized by equilibrium and dynamic surface tension measurements. Their micellization properties were investigated by steady-state fluorescence using pyrene as a probe and dynamic light scattering (DLS) techniques. The dependence of these properties on the alkyl chain length and the number of sugars was determined through a comparison with the corresponding monomeric surfactants CnMLA and previously reported sugar-based gemini surfactants containing monosaccharide gluconamide or disaccharide lactobionamide groups with a hexanediamide spacer. The critical micelle concentration (cmc) and surface tension of 2CnLac are both lower than those of CnMLA surfactants. These lower values indicate that the synthesized sugar-based gemini surfactants have excellent micelle-forming ability in solution and high adsorption ability at the air-water interface, which result from strong interactions of the hydrogen bonds between the hydroxyls in lactobionamide groups. When the alkyl chain length of 2CnLac increases to 14, premicellar formation occurs in the solution along with adsorption at the air-water interface at concentrations below the cmc. Furthermore, 2CnLac forms micelles measuring 4 to 12 nm in solution, with no dependence on the alkyl chain length, and their size slightly increases with increasing concentration.
