How chain length, headgroup polymerization, and anomeric configuration govern the thermotropic and lyotropic liquid crystalline phase behavior and the air-water interfacial adsorption of glucose-based surfactants

A matrix of anomerically pure glucose-based surfactants have been synthesized and their thermotropic and lyotropic liquid crystalline phase behavior, and air-aqueous solution interfacial adsorption were investigated. The surfactants, which represent the major components of the Fischer synthesis products, were the n-octyl, n-decyl and n-dodecyl homologues of alkyl alpha-D- and beta-D-glucoside and alkyl beta-D-maltoside. The matrix allowed the investigation of the effects of alkyl chain length, headgroup polymerization, and anomeric configuration on the surfactants' physicochemical properties. Increasing the alkyl chain length increases the hydrophobicity and the dispersion interaction between surfactant molecules, as one would expect, resulting in greater thermal stability of thermotropic and lyotropic phases. Phase transition temperatures are influenced significantly by the anomeric configuration in the shorter octyl derivatives, but to a lesser extent in the longer alkyl chain derivatives. The effect of increasing the degree of headgroup polymerization from one to two glucose units is to greatly increase the solubility of the surfactant in water and to increase the stability of the thermotropic liquid crystalline state. Changes in the headgroup polymerization and anomeric configuration have very little influence on the air-solution interfacial adsorption of these surfactants, while the effect of alkyl chain length variations was consistent with that expected from a thermodynamic consideration of surfactant self-assembly.