CRITICAL-DYNAMICS AND DIFFUSION BEHAVIOR OF POLYMER BLEND SOLUTIONS OF POLYSTYRENE POLY(METHYLMETHACRYLATE) D6-BENZENE/

The dynamic critical behavior of ternary mixtures of polystyrene (M(w) = 3.55 x 10(5))/poly(methylmethacrylate) (M(w) = 3.27 x 10(5))/deuter ated (d6-) benzene was investigated by quasielastic light scattering, pulsed-field-gradient nuclear magnetic resonance (PFG-NMR) and shear v iscosity measurements. The total polymer concentration c was fixed at c is-approximately-equal-to 12.9 . c (c* is the overlap concentration ), where polymer chains were weakly entangled. The relaxation rate GAM MA(I) of polymer composition fluctuations was separated to the critica l part GAMMA[c] and the background part GAMMA(b) GAMMA(c) was in good agreement with the Kawasaki function modified by Siggia, showing that the hydrodynamic backflow dominated over the diffusion as in binary fl uids of small molecules. The experimental mode-coupled region was much wider than the recent theoretical prediction by Roby and Joanny. The self-diffusion of constitutional polymers did not show any influence b y critical fluctuations in the present experimental time and length sc ales.