Molecular weight scaling in critical polymer solutions

In this letter we address the long-standing controversy which originated from differences between the experimental and theoretical values of the scaling exponent ( n ) for the critical amplitude ξ 0 of the correlation length in polymer solutions. Using small-angle neutron scattering we examine the dependence of ξ 0 on polymer molecular weight in polystyrene-methylcyclohexane-d 14 solutions. We find that the experimental values of n cr = 0.195 ± 0.010 in the critical region of phase demixing as well as n mf = 0.255 ± 0.009 in the mean-field domain around the Θ temperature agree with the predictions of scaling theory ( n cr = 0.185, n mf = 0.25).