engleski

Phase Behavior of Bis(Quaternary Ammonium Bromide)/Sodium Cholate/H2O System

Interactions in an oppositely charged surfactant mixture composed of a gemini surfactant, (bis(quaternary ammonium bromide)) and a bile salt (sodium cholate) in water have been studied at 30 oC. A combination of techniques was used including surface tension, conductometry, light scattering, light microscopy and microelectrophoretic measurements. A strong dependence of the phase behavior on the molar ratio and actual concentration of surfactants has been found. The interplay between electrostatic effects, geometry of molecules and dissimilar separation of the hydrophobic and hydrophilic moieties in the surfactants dictate the interaction mode and the microstructures formed. Instead of precipitation, in the equivalent mixtures formation of complexes, mixed micelles, vesicles, coacervates and solid crystalline phases have been observed. The extent of interacting forces in mixed micelles formed in equivalent mixtures has been evaluated by regular solution theory. A relatively high negative value of interaction parameter indicated a strong attractive interaction between surfactants. The compositions of both mixed micelles and mixed monolayer are found to be almost equimolar.

bile salts ; catanionic mixtures ; gemini surfactants

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