GENERALIZED HYDRODYNAMICS AND LANGEVIN-EQUATIONS FOR VISCOELASTIC BINARY-LIQUID MIXTURES

For viscoelastic binary liquid mixtures, generalised hydrodynamic equations are set up, in which the relaxation of the chemical potential due to structural relaxation is taken into account. A generalised diffusion equation is obtained, and the spectra of thermal fluctuations of concentration and mass density are derived. For very asymmetric mixtures of a mobile species in a very viscous solvent, such as a glass-forming liquid near its glass transition, coupled Langevin equations for concentration and mass density are derived, which may be applied to the calculation of the intensity of non-equilibrium fluctuations as observed in quench experiments.