Atomistic simulation of CO_2 solubility in poly(ethylene oxide) oligomers

摘要

We have performed atomistic molecular dynamics simulations coupled with thermodynamic integration to obtain the excess chemical potential and pressure-composition phase diagrams for CO_2 in poly(ethylene oxide) oligomers. Poly(ethylene oxide) dimethyl ether, CH_3O(CH_2CH_2O)_nCH_3 (PEO for short) is a widely applied physical solvent that forms the major organic constituent of a class of novel nanoparticle-based absorbents. Good predictions were obtained for pressure-composition- density relations for CO_2 + PEO oligomers (2 ≤ n ≤ 12), using the Potoff force field for PEO [J. Chem. Phys. 136, 044514(2012)] together with the TraPPE model for CO_2 [AIChE J. 47, 1676 (2001)]. Water effects on Henry's constant of CO_2 in PEO have also been investigated. Addition of modest amounts of water in PEO produces a relatively small increase in Henry's constant. Dependence of the calculated Henry's constant on the weight percentage of water falls on a temperature-dependent master curve, irrespective of PEO chain length.