MOBILITY OF SURFACTANTS AT THE WATER-IN-OIL EMULSION INTERFACE

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Abstract
The 13C NMR of water-in-oil emulsions and the mobility of the surfactant molecules present at the interfacial film, were estimated over a wide range of temperatures. Two different surfactant systems, sorbitan monooleate and 2-heptadecenyl-4,4(5H)-oxazoledimethanol (Alkaterge-T) were studied in water-in-oil type emulsions with benzene as the continuous medium. Abrupt changes in the mobility of surfactants at the interface were observed at about −5°C for Alkaterge-T and −10°C for sorbitan monooleate, considerably below the solidification point of the benzene continuous phase. A second abrupt change in mobility of the surfactant molecules was observed at −10°C for Alkaterge-T and at −20°C for the sorbitan monooleate. The changes were attributed to the onset of crystallization of the monolayer films and subsequent breakdown of emulsions. The results are consistent with the supercooling breakdown temperature of emulsions measured by low temperature differential scanning calorimetry.