Fluid Chromatography of Oligomers

Abstract

Gas chromatography at normal pressures is not used in the Separation of oligomers and polymers because large molecules do not possess sufficient vapor pressure. However, gas phases above their critical temperatures and at pressures from 20 to 200 bar, or higher, may possess the ability to dissolve large molecules. This property has long been known [1–2] and extends to many classes of Compounds, including inorganic salts. The dissolution ability is particularly pronounced with low-boiling solvents whose critical temperatures are low enough to ensure stability of the substrate, but at the same time high enough to indicate the possibility for sufficiently strong intermolecular forces between the supercritical solvent and the substrate molecules. When the density of the supercritical phase is high enough for sufficient solubility power, this density may still be considerably smaller than the density of the corresponding liquid just below the critical temperature.