A Force Field for Poly(oxymethylene) Dimethyl Ethers (OMEn).

A united atom force field for the homologous series of the poly(oxymethylene) dimethyl ethers (OMEn), H3C-O-(CH2O)n-CH3, is presented. OMEn are oxygenates and promising new synthetic fuels and solvents. The molecular geometry of the OMEn, the internal degrees of freedom, and their electrostatic properties were obtained from quantum mechanical calculations. To model repulsion and dispersion, Lennard-Jones parameters were fitted to the experimental liquid densities and vapor pressures of pure OMEn (n = 1-4). The critical properties of OMEn (n = 1-4) were determined from the simulation data. Additionally, the shear viscosity of pure liquid OMEn is evaluated and compared with literature data. Finally, the solubility of CO2 in OME2, OME3, and OME4 is predicted using a literature model for CO2 and the Lorentz-Berthelot combining rules. The results agree well with experimental data from the literature.