Coexistence curve and diameter of polystyrene in cyclohexane

We have measured the coexistence curve of a high-molecular-weight (Mw=1.56×10⁶) polystyrene in cyclohexane over a temperature range of 4×10^-5<(Tc-T)Tc<4×10^-2. The concentration difference X⁺-X^-, in volume fraction of polystyrene, was well represented by the expression ${X}⁺{-}{X}^{{-}}=B{{ε}}^{{β}}+{B}₁{{ε}}^{{β}+{Δ}}+{B}₂{{ε}}^{{β}+2{Δ}}$ based on the Wegner expansion, where ${β}=0.327±{}0.004$ and ${Δ}$ is fixed at 0.50. The concentration difference could also be well represented by the expression ${X}⁺{-}{X}^{{-}}=B{{ε}}^{{β}}+{B}^{{'}}{{ε}}^{{{β}}^{{'}}}$, where a somewhat higher value of ${β}$ was required. The diameter in the temperature range $4×{}{10}^{{-}5}<{({T}c{-}T)}{{T}c}<{10}^{{-}2}$ was represented by ${({X}⁺+{X}^{{-}})}{2}{-}{X}c=A{{ε}}^{{μ}}$, where ${μ}=0.860±{}0.006$. We have established, for the first time, the value of the asymptotic critical exponent ${β}$ of even a polymer system to be like that presently calculated for the Ising model. The observed exponent ${μ}(=1{-}{α})$ is consistent with results of specific-heat measurements.