PHASE-BEHAVIOR AND CHARACTERIZATION OF MICELLAR AND CUBIC PHASES IN THE NONIONIC SURFACTANT C[-17]E[84] WATER SYSTEM - A PFG NMR, SAXS, CRYO-TEM, AND FLUORESCENCE STUDY/

An extensive study of the diffusion behavior of the C[17]E[84]/water s ystem is presented. The surfactant, when mixed with water, forms a mic ellar phase below approximate to 13 wt% and a cubic phase between appr oximate to 20-60 wt % (at 25 degrees C). In addition to the pulsed Gel d gradient (PFG) NMR technique (used to determine the self-diffusion c oefficients), the system has been investigated by small-angle X-ray sc attering (SAXS), cryo-transmission electronmicroscopy (cryo-TEM), and time-resolved fluorescence quenching(TRFQ). The self-diffusion coeffic ient (D) and the transverse relaxation time (T-2) of the surfactant mo lecules decrease significantly when going from the micellar to the cub ic phase. The results of the PFG NMR, SAXS, cryo-TEM, and TRFQ experim ents show that the cubic phase is composed of discrete aggregates. On the basis of the rapid transverse H-1 NMR relaxation in the cubic phas e, it is argued that the micellar building blocks of the cubic phase a re nonspherical. Furthermore, the SAXS data for four different concent rations of the surfactant (25, 35, 45, and 55 wt %) in the cubic phase can be indexed to the space group Im3m. If the data from the NMR and the SAXS measurements are combined, a lifetime of the surfactant monom ers in the micelles of 8 and 7 ms was obtained at 25 and 35 wt % C[17] E[84], respectively.