The dynamic structure factor of a dilute solution of flexible polymer molecules in a binary mixture near the critical point is studied using mode coupling techniques. The strong concentration fluctuations of the solvent near the criticcal point lead to modifications of the hydrodynamic interactions between the monomer units in a chain. A set of equations is derived which describes the decay of the coupled solvent and polymer modes. The critical fluctuations of the solvent lead to a change in the wave vector dependence of the dynamic structure factor and a change in the center of mass diffusion coefficient of the polymer.
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