Beschreibung des Einflusses von Verzweigungen auf thermodynamische Stoffdaten mittels COSMO-RS und Molekularsimulation
Zusammenfassung der Projektergebnisse
COSMO-RS model has been successfully used to predict the vapor-liquid equilibrium in the systems including low generation dendrimers and hyperbranched molecules. Conformation analysis of large molecules leads to special difficulties in molecular modeling. Usually the size ofthe structures to be modeled allows only the application of the force field methods. Low generation dendrimers and hyperbranched molecules' conformational search and analysis in vacuum were performed, and a large amount of conformers have been obtained. But for the molecules studied here, the contributions from different conformers to the distribution of polarity of molecules or the activity coefficient appeared to be insignificant. This is in contradiction to findings in other research. The further DFT optimization is possible but not necessary. The easy and cheap single point calculation can be an alternative to a time-consuming DFT optimization. The conformation analysis in vacuum leads to overestimation of intramolecular stabilizations. The conformation analysis in the solvents will give more realistic information for the dendrimer or hyperbranched polymer solutions where strong polymer-solvent interactions influence the stability of the conformations. Compared to the different starting structures, the different branching degree or the type of the linear units, the end functional groups of the dendrimers or hyperbranched molecules have much stronger influence on the VLE in the systems studied, comprising dendrimers or hyperbranched compounds. The hyperbranched molecule structure can be tailored just by adding different end functional groups to meet a specific application with the systems. In the future the following aspects should be considered to investigate. 1. The force field for branching structures needs to be set up or improved, since the correct force field is the key point for an accurate molecular simulation. 2. Conformational search and analysis has been done in the dilute solutions. But the most experimental data are only available for the concentrated solutions. The dendritic structures in concentrated solutions should be investigated. 3. Very little research has been done for the very large systems using COMO-RS calculations. The Turbomole COSMO calculations failed for the dendritic molecules larger than 700 atoms using the latest version (version 5.9). Special treatment needs to be found to fix this problem.
Projektbezogene Publikationen (Auswahl)
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COSMO-RS and UNIFAC in Prediction of Micelle/Water Partition Coefficients. Ind. Eng. Chem. Res 2007,46,6501-6509
Liudmila Mokrushina, Matthias Buggert, Irina Smirnova, Wolfgang Arlt, Reinhard Schomäcker
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Potential of Branched Polymers in the Field of Gas Absorption: Experimental Gas Solubilities and Modeling. Ind. Eng. Chem. Res 2007, 46, 6572-6583
Jörn Rolker, Matthias Seiler, Liudmila Mokrushina, Wolfgang Arlt
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COSMO-RS Calculations of Partition Coefficients: Different Tools for Conformation Search. Chemical Engineering & Technology, Vol. 32. 2009, Issue 6, pp. 977–986.
Matthias Buggert, Cesar Cadena, Liudmila Mokrushina, Irina Smirnova, Edward J. Maginn, Wolfgang Arlt
