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

The C-13 NMR of water-in-oil emulsions and the mobility of the surfact ant molecules present at the interfacial film, were estimated over a w ide 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 contin uous medium. Abrupt changes in the mobility of surfactants at the inte rface were observed at about -5-degrees-C for Alkaterge-T and -10-degr ees-C for sorbitan monooleate, considerably below the solidification p oint of the benzene continuous phase. A second abrupt change in mobili ty of the surfactant molecules was observed at -10-degrees-C for Alkat erge-T and at -20-degrees-C for the sorbitan monooleate. The changes w ere attributed to the onset of crystallization of the monolayer films and subsequent breakdown of emulsions. The results are consistent with the supercooling breakdown temperture of emulsions measured by low te mperature differential scanning calorimetry.