Cluster Formation in Perfluoroheptane-i-Octane Systems near the Consolute Temperature

Abstract

Small‐angle x‐ray measurements on the system C₇F₁₆‐i‐C₈H₁₈ at temperatures near the consolute temperature show that a large degree of clustering takes place. Starting with pure i‐C₈H₁₈, which exhibits no scattering, the scattered intensity increases with increasing C₇F₁₆ concentration in a manner which indicates that the clusters are increasing in size. The maximum size is attained at a volume fraction of ∼0.50, at which point the clusters are made up of ∼140 C₇F₁₆ molecules. With a further increase in concentration, interaction peaks first appear in the intensity curves, indicating an approach to close packing, and then the slope of the curves begins to decrease, indicating that a phase reversal has taken place giving rise to smaller clusters of hydrocarbon in perfluorocarbon.