Molecular dynamics simulation of diffusion of gases in modified PEEK membranes

Molecular dynamics simulation of Diffusion of gases in modified PEEK membranes Elena Tocci, Maria Pia Perrone, Enrico Drioli IRMERC Institute on Membrane and Chemical Reactors - CNR c/o University of Calabria, Dep. of Chem. Eng. and Mater., I-87030 Arcavacata di Rende , Italy The establishment of correlations between the chemical structure of the polymers and their gas permeabilities/selectivities properties is a challenging task. The final goal is to generate the design rules for new and more performant polymeric materials. Molecular dynamics (MD) simulations were performed to study the transport coefficients of small gas molecules in amorphous modified cardo-poly(ether-ether-ketone) membrane materials (PEEK)s. The simulations have been carried out by using the Accelrys's (InsightII/discover) software together with the pcff and compass force fields applied for all the static and dynamic runs. The model packings consist of about 4500 atoms (60-80 residues) each. For the packing a new general methodology was developed consisting of four steps. The estimation of the diffusion coefficient D or the solubility S of small permeant molecules in a polymeric membrane are strongly depend on the quality of the amorphous cell used in the calculation. This, is particularly true in the case of stiff chain polymers containing aromatic moieties. Solubility, diffusivity and permeability coefficients have been calculated utilising the Gusev-Suter transition state Monte Carlo (MC) method. Good agreement between experimental and simulated results have been obtained for a number of polymeric materials.