The effects of adding alkyl sulfate surfactants to water-n-alkyl β-D-glucopyranoside (CmβG1) and water-alkyl ethylene glycol ether (CkOC2OCk)-CmβG1 mixtures are systematically explored. In a water-C10βG1-sodium decyl sulfate (SDeS) mixture, miniscule amounts of SDeS (SDeS:C10βG1 molar ratio of 0.0025) cause the upper miscibility gap of the water-C10βG1 mixture to vanish. Adding small amounts of alkyl sulfates to water-CkOC2OCk-CmβG1 mixtures increases the surfactant efficiency, shifts the single-phase microemulsion region to higher temperatures, and shrinks the three-phase region. These phenomenological phase behavior observations are explained in terms of electrostatic effects introduced by the addition of an ionic surfactant to nonionic micelles and monolayers. Small-angle neutron scattering (SANS) measurements from several D2O-CkOC2OCk-C mβG1-alkyl sulfate mixtures containing equal amounts of D2O and CkOC2-OCk are analyzed using a model for bicontinuous microemulsions. The values obtained from this analysis show that the monolayer spacing of D2O-CkOC2OCk-C mβG1-alkyl sulfate mixtures grows with increasing ionic surfactant concentration, and this increased spacing accounts for the observed increase in surfactant mixture efficiency.
|Original language||English (US)|
|Number of pages||8|
|Journal||Journal of Physical Chemistry B|
|State||Published - Sep 24 1998|