Ringförmige verbindungen – bessere lösungsmittel für makromoleküle als die entsprechenden linearen

Abstract

AbstractPolymers were dissolved in cyclic and linear compounds, in their di‐, tri‐ and n‐meres or in hydrocarbons, ethers, ketones, alcohols, chlorides and amines. Solutions of macromolecules in corresponding pairs of solvents exerted different activities, viscosities, and excess volumina. This result is explained by the measured diagrams of state or phases: For solutions of cyclic compounds the temperatures of experiments are farther away from those of phase separation; therefore, lower activities, higher viscosities, and smaller excess volumina are observed. From the larger area of infinite miscibility the common rule is derived that cyclic compounds are better solvents for macromolecules than the corresponding linear ones. The higher power of dissolution becomes evident considering the reduction of endgroups by polymerization as well as by cyclization. This compression of material increases density, viscosity, decreases cubic coefficient of expansion, compressibility and thus diminishes the difference between polymers and solvents. As the solubility parameter takes account of the more dense state of polymers, it is in many cases greater than that one of monomer or low molecular compound, which has to be adjusted to that of the polymer by cyclization. Recent thermodynamic calculations describe qualitatively the different dissolution power of cyclic and linear solvents by their different, P, V, T‐data.