Pressure effects on the Raman spectra of micelles: Pressure induced phase transition and structural changes in aqueous sodium oleatea)

Abstract

The Raman spectrum of an aqueous micellar solution of sodium oleate has been studied at pressures up to 5.05 kbar. It is shown that the acyl chain interactions are enhanced by pressure and that the number of gauche bonds in the micellar phase increases with increasing pressure. A first-order phase transition, from the micellar isotropic phase to a solidlike coagel phase was found to occur at 1.7 kbar. This phase transition has a very high pressure hysteresis. Significant differences were observed between the pressure and temperature effects on many structural properties of this aqueous sytem.