Precision Dilatometry of Microemulsions with Anionic Surfactants

Abstract

Density ρ , isothermal compressibility β í , and thermal expansion coefficient α are measured with high accuracy at 15 and 25 ° C for water-n -octane-sodium dodecyl sulfate-n -pentanol microemulsions with a water/oil weight ratio varying from 0.05 to 4. The internal pressure of the microemulsions is shown to be calculable from the results of dilatometric measurements. The phenomenon of temperature inversion is revealed for the temperature coefficient of internal pressure ∆ P i / ∆ T of the microemulsions. The analysis of this coefficient makes it possible to distinguish between three regions of the structural state in the microemulsions and a continuous structural transition in the associated microemulsions.

Effect of Alkyl Sulfate on the Phase Behavior of Microemulsions Stabilized with Monoacylglycerols

“…Moreover, the addition of ionic surfactants can reduce the sensitivity of the microemulsions stabilized by ethoxylated nonionic surfactants to temperature changes [36], and it has a great influence on the phase behavior [34][35][36][37][38]. SDS is a common very hydrophilic anionic surfactant often appearing in microand macroemulsion formulation, and those structures have been extensively studied by various methods [39][40][41][42]. In this context, we have studied the phase behavior of hexadecane/MAG:SDS/PG/water systems in a wide range of compositions by means of visual observation, FTIR spectroscopy and DSC techniques.…”

Heat capacity, conductivity, and structural changes of water-sodium dodecylsulfate-triethanolamine-1-pentanol-1,1,2,2-tetrafluorodibromoethane microemulsions

“…In order to obtain additional data on the structure of microemulsions the concentration and temperature dependences of their specific conductivity and specific isobaric heat capacity were determined. The conductivity is most often used to study the structural changes in surfactant micellar solutions and microemulsions [18,19], e.g., to find the critical concentration of surfactant micellization [20], the percolation threshold in w/o type microemulsions [18,[21][22][23][24]. It should be noted that apart from the conductivity, a change in the structure of microemulsions is usually accompanied by an abrupt change in viscosity [17,18,23], some bulk properties, the temperature coefficient of the internal pressure [24][25][26], and optical [27] properties of the microemulsions.…”

PVTx and vapor-pressure measurements of the quaternary water + n -octane + sodium dodecyl sulfate + 1-propanol solutions

“…The density and other thermodynamic properties (heat capacity, V isochoric heat capacity discontinuity criteria, was used to accurate determination phase-transition temperatures for each measured isochores. Volumetric properties, such as density, isothermal compressibility, thermal expansion coefficient of the same solutions were measured byKartsev et al [13]. for two temperatures of (288 and 298) K at atmospheric pressure for various concentrations of water and n-octane.…”