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Comparing gas transport in three polymers via molecular dynamics simulation

Abstract

People use polymers as materials for preparing separation media or containers. It is necessary to have a molecular level profound knowledge of gas transport in bulk and interface regimes of different polymers, but few researchers have done molecular level study of bulk and interface behavior of gases in several types of non-homologen polymers thoroughly or developed expressions to correlate gas transport properties with cavity size distribution and chain oscillation flexibility. Therefore, in the work, molecular dynamics (MD) simulation was employed to study transport of methane and n-butane molecules in the bulk and interface region of polyethylene (PE), poly (4-methyl-2-pentyne) (PMP) and polydimethylsiloxane (PDMS). Penetrant diffusivity, solubility and permeability in the bulk were studied firstly. The subdiffusion behavior of gas molecules is explored to obtain the mechanisms behind penetrant transport. Both penetrants have much smaller diffusivities in PE than in PMP and PDMS, and they have larger diffusivities in PDMS than in PMP. PE has lower accessible cavity fraction (ACF) and average oscillation amplitudes (AOAs) of chains than PDMS and PMP. PE also has much smaller solubilities and permeabilities of both penetrants than PDMS and PMP. Though the permeabilities of both penetrants in PDMS are higher than the corresponding values in PMP, PMP has higher selectivity of n-butane over methane than PDMS. Finally, nonequilibrium MD simulation was done to study the interface property and gas transport in the interface region, where the ratio of free volume are apparently higher than that in the bulk, offering penetrants more chances to get into the interface region from gas phase.

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Publication details

The article was received on 03 May 2018, accepted on 08 Aug 2018 and first published on 13 Aug 2018


Article type: Paper
DOI: 10.1039/C8CP02829J
Citation: Phys. Chem. Chem. Phys., 2018, Accepted Manuscript
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    Comparing gas transport in three polymers via molecular dynamics simulation

    L. Anderson, Q. Yang and A. Ediger, Phys. Chem. Chem. Phys., 2018, Accepted Manuscript , DOI: 10.1039/C8CP02829J

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