The effects of the variables of head group structure and salt concentration on microemulsions formed in mixtures of water, alkyl ethylene glycol ethers (C(k)OC2OC(k)), and n-alkyl β-D-glucopyranosides (C(m)βG1) are explored. Phase behavior of mixtures containing an anomer of the surfactant (n-alkyl α-D-glucopyranoside, C(m)αG1), or surfactants with long head groups (n-alkyl maltopyranosides, C(m)G2), or NaCl or NaClO4 as electrolyte are systematically reported as a function of temperature and composition. The substitution of n-alkyl α-D-glucopyranosides for n-alkyl β-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 C(m)G2 to water-C(k)OC2OC(k)-C(m)βG1 mixtures moves the phase behavior dramatically up in temperature when even small amounts of C(m)G2 are used. Adding a lyotropic electrolyte, NaCl, to water- C(k)OC2OC(k)-C(m)βG1 mixtures moves the phase behavior down in temperature, while the hydrotropic electrolyte NaClO4 moves the phase behavior up in temperature.
Bibliographical noteFunding Information:
This work was supported by ICI Surfactants.
- Alkyl polyglucosides
- Krafft boundary
- Phase behavior