AGGREGATE SIZE AND SURFACTANT HYDROCARBON DIFFUSION IN THE CUBIC PHASE OF THE SODIUM OCTANOATE/HYDROCARBON/WATER SYSTEM/

The cubic liquid crystalline (I-1) phase formed by sodium octanoate, n -octane, and water (40.0:4.0:56.0% by weight) was studied by means of a fluorescence quenching (FQ) technique. Time resolved fluorescence wa s measured for small amounts of solubilized pyrene (P), both with and without a solubilized quencher (Q), dimethylbensophenone. The FQ data show that the Q and P molecules are captured in closed amphiphilic agg regates consisting of ca. 75 sodium octanoate molecules at 298 K. From these results together with already published X-ray data the number o f micelles per unit cell was estimated to be eight. NMR self-diffusion studies of the surfactant and the hydrocarbon were carried out on the above mentioned cubic phase as well as on the corresponding phases fo rmed with p-xylene and cyclohexane. These experiments convey informati on on the lifetime of the surfactant and the hydrocarbon in the aggreg ates and also on the structure of the cubic phase. (C) 1996 Academic P ress, Inc.