A model low-molecular-weight polymer mixture was studied as a function of temperature near the critical point by small-angle neutron scattering (SANS) and dynamic light scattering (DLS). SANS measurements reveal a crossover in the static susceptibility from mean-field to non-mean-field behavior at ${\mathit{T}}_{\mathit{x}}$≃${\mathit{T}}_{\mathit{c}}$+30 °C, in quantitative agreement with the Ginzburg criterion. This crossover behavior is also reflected in the DLS experiments, which reveal mode-coupled critical dynamics far into the mean-field regime.

• Received 23 April 1990

DOI:https://doi.org/10.1103/PhysRevLett.65.1893