| Research Abstract |
We have been improving a neutron spin echo (NSE) spectrometer at C_<2-2> port of JRR-3M, JAERI.A high-pressure cell for NSE studies in comlex fluids was installed using this grant.
NSE and small angle scattering experiments have been performed to study the slow dynamics such as membrane undulation in complex fluids involving amphiphiles. Intermediate correlation functions I(Q,t) obtained from our NSE experiments were well fitted to the equation I(Q,t)=I(Q,0)exp[(-Gt)^<2/3>] for the dipalmitoylphosphatidylcholine (DPPC)-water-CaCl_2 system and for the low temperature and high temperature bicontinuous microemulsion phases and the lamella phase of the non-ionic surfactant C_<12>E_5/n-octane / water system, and also for the dense droplet phase of, the temperature-induced and the pressure-induced lamella phases of the ionic surfactant AOT / n-decane / water system. The relaxation rate G increased as Q^3. From these results, the theory of Zilman and Granek, in which they use the Helfrich bending free energy to describe membrane undulations in sponge and lamellar phases, was first supported by our NSE experiments. We estimated the bending modulus of the membranes using their theory. For aqueous solutions of non-ionic surfactant C_<16>E_7 with wormlike micelles, the results that I(Q,t)=I(Q,0)exp[(-Gt)^<3/4>] and G increased as Q^<8/3> are also explained by their theory for 1-dimensional polymer-like model.
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