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Interfacial instability and spontaneous formation of microemulsions
Author(s) -
Shah D. O.,
Tamjeedi A.,
Falco J. W.,
Walker R. D.
Publication year - 1972
Publication title -
aiche journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.958
H-Index - 167
eISSN - 1547-5905
pISSN - 0001-1541
DOI - 10.1002/aic.690180605
Subject(s) - microemulsion , surface tension , hexadecane , birefringence , chemistry , phase (matter) , chemical physics , chemical engineering , phase transition , materials science , analytical chemistry (journal) , thermodynamics , optics , pulmonary surfactant , chromatography , organic chemistry , biochemistry , physics , engineering
Microemulsions, which are optically transparent oil‐water dispersions, were spontaneously produced upon mixing hexadecane, hexanol, potassium oleate, and water in specific proportions. The drop‐volume measurements of hexadecane‐water interface in the presence of hexanol or potassium oleate revealed that these surfactants decrease the interracial tension of the hexadecane/water interface. It is proposed that the interaction between these two emulsifiers at the oil‐water interface causes spontaneous negative interfaical tension resulting in interfacial instability and the formation of microemulsions. As the amount of water is increased, the microemulsion exhibits a clear to turbid to clear transition. Unlike the clear regions, the turbid region possesses birefringence. The development of birefringence is also accompanied by a sharp decrease in electrical resistance. High‐resolution (220 Mc) nuclear magnetic resonance data suggest that water exists in two distinct environments or structures in the birefringent region. The electrical, birefringence, and nuclear magnetic resonance data agree with the proposed mechanism of phase‐inversion of microemulsions, which can be described as water spheres to water cylinders to water lamellae to a continuous water phase. The spontaneous formation of such structures (for example, water cylinders and lamellae) presumably depends upon the phase‐volume ratio and the interfacial tension at the oil‐water interface.