Turbidity of critical solutions of polymethylmethacrylate in 3-octanone

We have measured the turbidity for a series of solutions of polymethylmethacrylate in 3-octanone ~PMMA/3-OCT! with various polymer molecular weights. The obtained correlation length ~j! and the osmotic compressibility ~x! show power law dependence on both the reduced temperature e 5(T2Tc)/Tc and the degree of polymerization N of the polymer chains, i.e., j;N e and x;Ne, with the associated scaling exponents in good agreement with theoretical predictions. When the results of the present experiment are combined with those from an earlier coexistence curve measurement @K.-Q. Xia, X.-Q. An, and W.-G. Shen, J. Chem. Phys. 105, 6018 ~1996!#, it is found that the concept of two-scale-factor universality applies to systems consist of the same polymer/solvent pair but with different molecular weights. © 1997 American Institute of Physics. @S0021-9606~97!51030-0#