DYNAMICAL BEHAVIOR OF MICROEMULSION AND SPONGE PHASES IN THERMAL-EQUILIBRIUM

The dynamical behavior of microemulsion and sponge phases is studied w ith a time-dependent Ginzburg-Landau model. The model has been shown p reviously to capture many of the essential static properties of these systems. Using a field-theoretic perturbation theory, we calculate the frequency-dependent (complex) viscosity eta(omega), sound velocity c( omega) and damping D(omega), and the scattering intensity S(k,t) in bu lk and film contrast. The viscosity is almost frequency independent fo r small omega, then drops sharply at a characteristic frequency omega , corresponding to a characteristic relaxation time tau similar to 1/o mega. The same relaxation rime is also found to dominate the sound ve locity and damping. The characteristic frequency has the scaling form omegasimilar to xi(-6)Omega(q xi), where xi is the correlation length and q is the inverse domain size of the microemulsion structure. The scattering intensity S(k,t) decays exponentially in time t for large t with an algebraic prefactor t(-alpha), both in bulk and in film contr ast. In the latter case, we find there are several regimes of the wave vector k with different exponents alpha.