Gas Transport in Dense Polymeric Membranes, Molecular Dynamics Simulations

Abstract

Classical simulations such as molecular dynamics (MD) are powerful tools to either complement experimental evidence or to predict gas transport properties in polymers. They can reproduce the gas uptake curves and characterize at the molecular level both the mechanisms of gas mobility and the structural and dynamical changes of the matrices. It is also possible to evaluate the gas diffusion and solubility coefficients, thus leading to model permeabilities. However, realistic fully atomistic simulations are currently restricted to the 10 −9 to 10 −7 s timescale, which is hardly compatible with the longer relaxations of high molecular weight polymers and the establishment of the Fickian diffusion regime for slowly diffusing gases. Consequently, pure MD will often have to be coupled with other simulation techniques in order to overcome these shortcomings, both during the model preparation procedures and the analyses of gas transport.

Structure and Properties of High and Low Free Volume Polymers Studied by Molecular Dynamics Simulation

“…During the last decade, atomistic modeling using molecular dynamics (MD) [1,2] has become an efficient tool for the elucidation and prediction of various properties of polymers and, in particular, potential and applicable materials for gas and vapor separation membranes. Free volume and size distribution of free volume elements (FVEs) [3][4][5][6], energy barriers of inner rotation of the main chains [4,7,8], gas diffusion, solubility and permeability coefficients in polymers [3,5,7,9], gas and vapor sorption isotherms [10][11][12] can all be evaluated and predicted by MD in polymers with various chemical structures.…”

Diffusion of low‐molecular‐weight permeants through semi‐crystalline polymers: combining molecular dynamics with semi‐empirical models

“…Now, the diffusion coefficient ( D ) can be estimated from MD simulations using Eqn (1), where t is the simulation time and the term in the angled brackets is known as the mean squared displacement (MSD): …”

“…2 MD simulations are now widely and routinely applied in fields ranging from packaging to materials science, biophysics, biosensor fabrication, reverse osmosis and gas separation. 3 Now, the diffusion coefficient (D) can be estimated from MD simulations using Eqn (1), where t is the simulation time and the term in the angled brackets is known as the mean squared displacement (MSD) [4][5][6][7] :…”

Molecular characterization of polyOAPS-imide isomer hyper-cross-linked membranes: Free-volume morphologies and sorption isotherms for CH4 and CO2

“…In molecular simulations of dense matrices, the free-volume or voidspace can be characterized using different techniques [23,43,90,91]. A simple geometric approach is the percentage of probe-accessible volume, %PAV, which is obtained by repeated random trial insertions of a virtual spherical probe of predefined radius [92].…”