Abstract
Temperature dependent phase behavior of Pseudo-ternary Thiourea X-100 + 1-hexanol (1:5 molar ratios)/oil/water systems is reported. The influence of nature of hydrocarbon oil and type of electrolytes (weak as well as strong) has been investigated on the temperature induced phase behavior of the ternary system. At surfactant concentration, Φs = 40%, a “nose shaped” microemulsion region is observed. Below one-phase microemulsion region, Lα phase appears. The presence of NaCl decreases the domain size of 1Φ micellar region whereas oxalic acid first decreases the domain below Φw 18 in the lower boundry of the phase diagram. The critical weight fraction of water, Φwcri decreases in presence of both electrolytes. However, Φwmax increases in presence of oxalic acid and remains constant in presence of NaCl as compared to salt free system. Furthermore, when cyclohexane was replaced by a longer straight chain hydrocarbon, dodecane, the domain of the one-phase microemulsion region is tremendously increased.
Highlights
Microemulsions (MEs) are optically transparent, thermodynamically stable, nano-structured mixture of oil and water stabilized by surfactant and co-surfactant [1]
The critical weight fraction of water, Φwcri decreases in presence of both electrolytes
Constructing a Pseudo-Ternary Phase Diagram Phase diagram of Thiourea X-100 +1-hexanol (1:5 molar ratio)/oil/water or aqueous electrolyte systems were constructed by titration method and the phase boundaries of one-phase micellar region of the ternary systems were determined at fixed surfactant concentration, γ = 40%
Summary
Microemulsions (MEs) are optically transparent, thermodynamically stable, nano-structured mixture of oil and water stabilized by surfactant and co-surfactant [1]. Phase behavior and structural organization of microemulsions are known to play key roles in its industrial and technological applications. Phase behavior studies provide information on the phase boundaries of different phases as a function of composition and temperature and more important structural organization of surfactant aggregates can be interred [3]. It allows comparison of efficiency of different surfactant for a given application. Long equilibration is required in multiphase regions especially if a liquid crystalline phase is involved and this makes phase determination tedious, time consuming, and difficult [1,2, 4]
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