Effects of solubilized dodecylamine on the microstructure of cetylpyridinium bromide-n-butanol-hexane-water system studied by pulsed-gradient spin echo NMR and ESR spin label methods

The effect of solubilized dodecylamine (DDA) on the structure of the cetylpyridinium bromide-n-butanol-hexane-water microemulsions has been studied by the Fourier-transform pulsed-gradient spin-echo¹H nuclear magnetic resonance and the electron spin resonance spin label method. The sample compositions were chosen to examine three different microemulsion structures: oil-in-water, water-in-oil and bicontinuous. In all systems the DDA molecules are shown to be incorporated into the oil-water interface, resulting in essential changes in the microemulsion structure. In the micellar systems the DDA emergence in the interface causes an increase of the micelle size and a redistribution of butanol and water between micelle and bulk phases. In the oil-in-water microemulsions of amine-containing systems the quantity of micellized butanol and water decreases. In the water-in-oil microemulsions the introduction of DDA leads to an increase of butanol and water involved in the micelle formation. The redistribution of butanol and water between polar and organic phases in the microemulsions would be expected to cause changes in the bicontinuous structure.