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 I C −1 ∝(T − T sp ) γ with γ = 1.26 ± 0.08 . The long‐range correlation length ξ s obeys a relation ξ s ∝(T − T sp ) −ν s with ν s = 0.62 . The extrapolated linewidth obeys a relation lim K→0 (Γ / K 2 )∝(T − T sp ) γ * with γ* ≈ 1 at the concentration exhibiting the maximum phase separation temperature (T p,max ) , and γ* ≈ 0.77 at the critical solution concentration (T sp = T c ) . The long‐range correlation length of the critical concentration solution obeys a relation ξ Γ ∝(T − T c ) −νΓ with ν Γ ≈ 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.