Light Scattering Investigations of Binary Liquid Mixtures in the Presence of Polymers and Gels.

Both static and dynamic light scattering experiments were carried out on a system of gels saturated with solvents which were binary liquid mixtures and on a system of polymers dissolved in binary mixtures. In the gel experiment, drastic changes of critical behavior from that of a pure binary mixture and extremely long relaxation times to thermal equilibrium have been observed; specifically, a temperature-dependent dynamic crossover length is found in the dynamic measurement and a temperature-independent characteristic length and temperature dependent amplitude are obtained from the static structure factor measurement. These results are compared with recent theories on the random field Ising models. In the second experiment, properties near the binary fluid critical point have been found to be qualitatively the same as those for the pure solvent case. Also, there is evidence that the appropriate parameter to describe the system may be monomer concentration rather than polymer concentration.