Untersuchungen des Flüssig-Flüssig Phasenübergangs von Lösungen Ionischer Flüssigkeiten mit dem Trifluormethylsulfonat-Anion

Phase separations of solutions of ionic liquids of the type Alkylmethylimidazolium Trifluoromethylsulfonate (Cnmimtfo) with different lengths of alkyl side chains (n=4,5,6,7,8) were investigated in various solvents. Phase diagrams were analysed for solutions in water, dioxane and weakly polar arene-halides using a function that presumes Ising critical behavior and takes the asymmetry of the phase diagrams into account. The phase diagrams are in agreement with the theorem of corresponding states. Comparison with the model system of charged hard spheres in a dielectric continuum (restricted primitive model; RPM) is made. The RPM critical temperatures depend linearly on the dielectric constant of the solvents. Two systems were selected (C6mimtfo-Chlorobenzene and C8mimtfo-4Chlortoluol) for studies of the critical behavior with mK-accuracy of viscosity, refractive index, static and dynamic light scattering and theoretical analysis. The measurements prove Ising behavior with deviations indicating normal crossover to mean-field criticality.