Phase- and Interfacial Behavior of hyperbranched aqueous polymer solutions

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Hyperbranched polymers with a tree-like structure are strongly branched, polydisperse macromolecules with a large number of polar terminal groups. Based on their unique properties several potential application areas, such as environment-friendly solvent for distillation, extraction or CO2-capture or as drug-delivery system in medicine, in food technology and in cosmetics are discussed. For all of these purposes the liquid-liquid equilibria (LLE) as well as the interfacial properties play an important role. In the last research project a new model based on Lattice-Cluster-Theory (LCT) in combination with two different association models for the description of the demixing behavior of aqueous hyperbranched polymer solutions was developed. The experimental cloud point curve could by modeled with satisfactory accuracy. The first association model describes the association as strong physical interaction (Wertheim theory) and the second one as chemical equilibrium (E-CALM). Both association models are able to account for cross association occurring between the solvent, usually water, and the polar terminal groups of the polymer and the self-association of the solvent and/or the polymer. The combined model allows the direct use of the polymer architecture in the thermodynamic equations without any additionally adjustable parameter. However, the most important disadvantage of the model in its current state is the negligence of the polydispersity of the hyperbranched polymer. Therefore, the actual scheduled research project aims to solve this issue. To the first time the influence of the polydispersity with respect to the molecular weight using continuous thermodynamics should by investigated theoretically. Beside to the phase equilibria also the interfacial properties are in focus of interest. Until now, the modeling of interfacial properties with help of the density gradient theory for inhomogeneous systems, where an interface is present, is limited to ternary systems. The theory should be generalizes in order to describe the interfacial properties of polydisperse polymers in a single solvent. This generalized theory will permit the study of interfacial enrichment, especially the question, if short-chain polymers or long-chain polymers will be preferential enriched in the interface will be answered. Caused by the high viscosity of polymers having a large molecular weight the answer of this question has a large impact on the material transfer over the interface. The theoretical frameworks will be developed for aqueous hyperbranched polymer solution. Additionally, the thermodynamic properties of solution composed of hyperbranched polymers and alcohol (1-propanol and 2-propanol) will be investigated. Using this approach the transferability of the models will be investigated in detail.