CONCENTRATION FLUCTUATION IN A POLYMER MIXTURE

The critical behavior in a mixture of polystyrene and polymethylphenylsiloxane has been examined by the angular distribution of the scattered light intensity over 5.7 < k < 19.6 mum-1 and 0.045 < T- T(c) < 2.4-degrees-C, where k is the scattering wave number and T(c) is the critical mixing temperature. The osmotic compressibility obeys a relation chi(T) approximately (T-T(c))-gamma with gamma=1.22+/-0.02 and the long-range correlation length xi approximately (T-T(c))-nu with nu=0.62+/-0.02, in good agreement with the three-dimensional Ising-model universality.