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 synthesiz ed and their thermotropic and lyotropic liquid crystalline phase behavior, and air-aqueous solution interfacial adsorption were investigated. The surf actants, which represent the major components of the Fischer synthesis prod ucts, 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 inv estigation 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 disp ersion interaction between surfactant molecules, as one would expect, resul ting in greater thermal stability of thermotropic and lyotropic phases. Pha se transition temperatures are influenced significantly by the anomeric con figuration in the shorter octyl derivatives, but to a lesser extent in the longer alkyl chain derivatives. The effect of increasing the degree of head group polymerization from one to two glucose units is to greatly increase t he solubility of the surfactant in water and to increase the stability of t he thermotropic liquid crystalline state. Changes in the headgroup polymeri zation and anomeric configuration have very little influence on the air-sol ution interfacial adsorption of these surfactants, while the effect of alky l chain length variations was consistent with that expected from a thermody namic consideration of surfactant self-assembly.