Coexistence curve of polystyrene in methylcyclohexane. III. Asymptotic behavior of ternary system near the plait point

Coexistence curve measurements were made on the systems of polystyrene (PS) in methylcyclohexane (MC) by using the refractive index method. The entire shape of the coexistence curve of the ternary system PS I(Mw=1.72×104)–PS II(Mw=7.19×105)–MC with ξ2=0.1704 is very different from those of the binary systems PS(I)–MC and PS(II)–MC, where ξ2 denotes a volume fraction of PS(II) to total polystyrene. The asymptotic shape of the ternary coexistence curve near the critical point was found to be characterized by the exponent βt=0.384±0.004, which is close to the fully renormalized critical exponent. The direction of tie lines near the critical point was found to be parallel to each other from the calculation with the classical empirical equation of the Gibbs free energy.