CRITICAL EXPONENTS AND PHASE-DIAGRAM OF POLYMER BLEND SOLUTIONS - POLYSTYRENE POLY(METHYL METHACRYLATE) D(6)-BENZENE SYSTEM/

Critical behaviour of blend solutions of polystyrene (M(w) = 3.55 x 10 (5)/poly(methyl methacrylate) (M(w) = 3.27 x 10(5)) in d6-benzene was investigated by static light scattering. The phase diagram (spinodal, binodal and cloud points) was determined at a fixed total polymer conc entration. The system had the lower critical solution temperature. The inverse isothermal osmotic compressibility (partial derivative pi/par tial derivative c1)T and correlation length xi of concentration fluctu ations were determined as functions of the reduced temperature epsilon = \T(s)/T-1\ near the stability limit, where T is the absolute temper ature and T(s) is the spinodal temperature. Both (partial derivative p i/partial derivative c1)T and xi were described by single exponents ov er the investigated temperature range. The critical exponents gamma an d nu for (parital derivative pi/partial derivative c1)T and xi were 1. 23 and 0.63, respectively. They were very close to the three-dimension al Ising exponents and obviously different from the mean-field or Fish er's renormalized Ising exponents, as theoretically predicted by Brose ta et al.