Partition Coefficients of Organic Molecules in Squalane and Water/Ethanol Mixtures by Molecular Dynamics Simulations

Research output: Research - peer-reviewJournal article – Annual report year: 2011

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Accurate partition coefficient data of migrants between a polymer and a solvent are of paramount importance for estimating the migration of the migrant over time, including the concentration of the migrant at infinite time in the two solvents. In this article it is shown how this partition coefficient can be estimated for both a small hydrophilic and a hydrophobic organic molecules between squalane (used here to mimic low density poly ethylene) and water/ethanol solutes using thermodynamic integration to calculate the free energy of solvation. Molecular dynamics simulations are performed, using the GROMACS software, by slowly decoupling of firstly the electrostatic and then the Lennard–Jones interactions between molecules in the simulation box. These calculations depend very much on the choice of force field. Two force fields have been tested in this work, the TraPPE-UA (united-atom) and the OPLS-AA (all-atom). The computational cheaper TraPPE-UA force field showed to be more accurate over the whole range of systems compared to the OPLS-AA force field. Moreover, some of the calculations were done with five different water models to investigate the influence of the specific water model on the calculations. It was found that the combination of the TraPPE-UA force field and the TIP4p water model gave the best results. Based on the methodology proposed in this article, it is possible to obtain good partition coefficients only knowing the chemical structure of the molecules in the system.
Original languageEnglish
JournalFluid Phase Equilibria
Volume306
Issue number2
Pages (from-to)162-170
ISSN0378-3812
DOIs
StatePublished - 2011
CitationsWeb of Science® Times Cited: 2

    Research areas

  • Polymer, Molecular Dynamics, Partition coefficient, Free energy calculations
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