Thermodiffusion of ternary polymer solutions

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Ternary mixtures are prototypic for truly multicomponent systems, since they show characteristic cross coupling phenomena that are still absent in binary mixtures. We want to investigate thermodiffusion in ternary mixtures containing at least one polymeric component. By studying a polymer in a mixed solvent we want to investigate the coupling and decoupling of the solvent-solvent and the polymer-solvent dynamics. By increasing the molar mass of the polymer we will be able to study the transition from a commensurate ternary mixture, composed of similar-sized molecules, to an incommensurate system with a pronounced size asymmetry of the constituents. Based on the envisaged experiments, on our previous work on the thermophobicity concept, and on results for binary polymer solutions and blends, we will extend the thermophobicity model to ternary mixtures and investigate the feasibility of an effective solvent approach for a polymer in a mixed solvent. We will also establish polymers in mixed solvents as fully characterizable model systems for ternary liquids. Contrary to mixtures of small molecules, a clear separation of the eigenvalues of the diffusion matrix can be expected, which will allow for a unique determination of all six independent diffusive transport coefficients of a non-isothermal ternary mixture. The experimental work will be complemented on the theoretical side by an intense collaboration with K. Morozov (Technion Haifa), who will extend his existing model for hard spheres to flexible chain molecules and ternary mixtures using the PC-SAFT equation of state and data from the experimental part of the project.