The Effect of Anomeric Head Groups, Surfactant Hydrophilicity, and Electrolytes on n-Alkyl Monoglucoside...

The effects of the variables of head group structure and salt concentration on microemulsions formed in mixtures of water, alkyl ethylene glycol ethers (CkOC2OCk), and n-alkyl beta-d-glucopyranosides (CmbetaG1) are explored. Phase behavior of mixtures containing an anomer of the surfactant (n-alkyl alpha-d-glucopyranoside, CmalphaG1), or surfactants with long head groups (n-alkyl maltopyranosides, CmG2), or NaCl or NaClO4 as electrolyte are systematically reported as a function of temperature and composition. The substitution of n-alkyl alpha-d-glucopyranosides for n-alkyl beta-d-glucopyranosides causes precipitation under some conditions in all mixtures studied. These solubility boundaries begin in the water-surfactant binary mixture at the Krafft boundary, then extend to high concentrations of both surfactant and oil. Increasing the effective length of the surfactant head group by adding CmG2 to water-CkOC2OCk-CmbetaG1 mixtures moves the phase behavior dramatically up in temperature when even small amounts of CmG2 are used. Adding a lyotropic electrolyte, NaCl, to water-CkOC2OCk-CmbetaG1 mixtures moves the phase behavior down in temperature, while the hydrotropic electrolyte NaClO4 moves the phase behavior up in temperature. Copyright 1999 Academic Press.