Experimental and Theoretical Investigation of an Aqueous Two Phase System with a Hyperbranched Polymer

基于双水相体系（ATPS）的溶解间隙的萃取是浓缩蛋白质的主要可能性。这些系统由适当的聚合物、盐组成。该研究项目的基本思想是通过超支化聚酯酰胺与右旋糖酐结合形成ATPS来应用材料基础。该ATPS的特性进行了比较与经典的ATPS组成的PEG 8000和葡聚糖。与线性聚合物不同，超支化聚合物具有不同的官能团和不同的结构，这些官能团和结构影响热力学行为和相容性间隙。超支化聚合物在流体分离中的另一个优点是与线性聚合物相比粘度低。在这两个ATPS的分配L-丝氨酸上的两个共存相进行了实验研究。作为萃取基础的相平衡的建模可以通过热力学模型来实现，该热力学模型实现了超支化聚合物的聚合物结构和官能团。热力学模型是晶格集团理论（LCT）结合Wertheim理论。通过应用开发的热力学模型，它是可能的预测分配的L-丝氨酸的两个ATPS的阶段，通过调整模型参数的二元分别三元子系统。作为后续步骤，开发的热力学模型将被用来调查两个ATPS的界面现象，如界面张力或跨界面的传质。这些现象的建模将进行开发的模型与密度梯度理论（DGT）相结合。DGT给出了非均匀系统的亥姆霍兹能的表达式。因此，可以计算平衡时的界面张力，并提供化学势的表达式，从而可以计算传质。除了建模的界面张力和跨界面的传质将实验确定。对于本研究，将使用旋转液滴法测定界面张力，并使用Nitsch-celle研究界面上的传质。如果这一项目获得成功，除了大大扩展ATPS的物质基础外，还将提供一个包括相平衡和传质在内的描述ATPS的封闭理论。

Extraction which is based on the miscibility gap of aqueous two phase systems (ATPS) is a principal possibility to concentrate proteins. These systems are composed by adequate polymers, salts. The fundamental idea of this research project was the extension of the material base by the application of hyperbranched polyesteramid in combination with dextran to form an ATPS. The characteristics of this ATPS were compared with a classical ATPS composed of PEG8000 and dextran. In contrast to linear polymers hyperbranched polymers with different functional groups and different architectures which influence the thermodynamic behaviour and the miscibility gap can be synthesized. A further advantage of hyperbranched polymers in fluid separation is the low viscosity compared to linear polymers. In both ATPS the partitioning of L-serin on the two coexisting phases was experimentally investigated. The modeling of the phase equilibria which are the basis of the extraction can be realized by a thermodynamic model which accomplishes for the polymer architecture and the functional groups of the hyperbranched polymer. The thermodynamic model is the Lattice Cluster theory (LCT) combined with the Wertheim Theory. By the application of the developed thermodynamic model it was possible to predict the partitioning of L-serin on the phases of both ATPS by an adjustment of the model parameters to binary respectively ternary subsystems. As a subsequent step, the developed thermodynamic model will be used to investigate interfacial phenomena of both ATPS such as interfacial tension or mass transfer across the interface. The modelling of these phenomena will be conducted by the combination of the developed model with the density gradient theory (DGT). The DGT gives an expression for the Helmholtz Energy of an inhomogeneous system. Therefore, it is possible to calculate the interfacial tension in equilibrium and to provide an expression for the chemical potential which allows calculating the mass transfer. In addition to the modelling the interfacial tension and the mass transfer across the interface will be experimentally determined. For this investigation, the spinning drop method will be used to determine the interfacial tension and a Nitsch-celle will be used to investigate the mass transfer across the interface. If this project is successful, a closed theory for the description of ATPS including phase equilibria and mass transfer would be provided in addition to the considerably extension of the material base of ATPS.