Hyperbranched polymers as phase forming components in aqueous two-phase extraction

This work focusses on the experimental and theoretical investigation of the partitioning of a l-serine in an aqueous two-phase system (ATPS) based on a hyperbranched polymer. As a model ATPS, a polymer system containing a hyperbranched polyesteramide and dextran was chosen. The partitioning of l-serine in this ATPS was studied and compared with the partitioning of l-serine in a conventional ATPS consisting of polyethylene glycol (PEG) and dextran. For the thermodynamic modelling of these ATPS's the Lattice Cluster Theory (LCT) in combination with the Wertheim association theory was used. The LCT allows the incorporation of the hyperbranched polymer architecture in the Helmholtz free energy and the Wertheim association theory considers the influence of the polar groups. As a result, it can be stated that in both ATPS, l-serine is mainly partitioned into the dextran-enriched phase, but in the ATPS based on the hyperbranched polyesteramide and dextran, the l-serine concentration in the dextran-enriched phase is higher. The partitioning of l-serine could be predicted by the used thermodynamic model on basis of the solubility experiments carried out for l-serine in aqueous solutions of phase forming components. Further, this work represents the first application of the used thermodynamic model on a quaternary system.