Intensity and Linewidth Studies of the System Polystyrene–Cyclohexane in the Critical Region

Abstract

The cloud-point curve and critical opalescence of the system polystyrene (Mn = 392 000)–cyclohexane have been investigated. The critical point, as determined by the phase-volume ratio method, is at a higher concentration than the maximum in the cloud-point curve. Experiments are reported on the angular and the spectral distribution of scattered light for a solution of composition corresponding to the maximum in the cloud-point curve and on the spectral distribution for a solution of critical concentration. The temperature dependence of the extrapolated zero-angle scattered intensity obeys a relation lim K→0 IC−1∝(T − Tsp)γ with γ = 1.26 ± 0.08. The long-range correlation length ξs obeys a relation ξs∝(T − Tsp)−νs with νs = 0.62. The extrapolated linewidth obeys a relation lim K→0 (Γ / K2)∝(T − Tsp)γ* with γ* ≈ 1 at the concentration exhibiting the maximum phase separation temperature (Tp,max), and γ* ≈ 0.77 at the critical solution concentration (Tsp = Tc). The long-range correlation length of the critical concentration solution obeys a relation ξΓ∝(T − Tc)−νΓ with νΓ ≈ 0.58. Various exponents as compared with the corresponding values for one- and two-component systems show that the critical exponent concept and the spinodal generalization are equally applicable to multicomponent (polymer) systems.