Molecular Dynamics Simulation of Gas Transport in Amorphous Polyisoprene

Abstract

Molecular dynamics (MD) simulations were performed to study the transport properties of gases (oxygen, nitrogen, and methane) in amorphous cis-1,4-polyisoprene over a wide range of temperatures. The COMPASS force field was used as the molecular mechanics force field in the simulations. Experimental values of density and glass transition temperature were successfully reproduced using the atomistic potentials determined by COMPASS. Diffusion coefficients were determined from long NVT simulation times (up to 3 or 1.5 ns) in the temperature range of 278-378 K. The diffusion coefficients calculated from the Einstein relationship agree well with available experimental data. Further studies on the temperature dependence of diffusion coefficients indicate that curvature is observed in the Arrhenius plot of diffusivity versus inverse temperature for methane, but the plots are linear over the investigated temperature range for oxygen and nitrogen. These simulation results are useful to understand the temperature dependence of diffusion coefficients, and provide a basis for the determination of diffusion coefficients at high temperatures and the modeling of thermo-oxidative degradation of polyisoprene.

Investigation of the diffusion and permeation of several media molecules in nano‐sealing composites using molecular dynamics simulation

“…Due to the long‐term and microscopic characteristics of the diffusion and permeation of small molecules in materials, simulations have received growing attention [8–18]. Simulations effectively eliminate the problems of long experimental times and measurement difficulties.…”

“…Wu et al [7] studied the penetration of dimethyl ether in sealing materials and pointed out that the experiment to determine the diffusion coefficient required sophisticated equipment and measurement technology and a long time period. Due to the long-term and microscopic characteristics of the diffusion and permeation of small molecules in materials, simulations have received growing attention [8][9][10][11][12][13][14][15][16][17][18]. Simulations effectively eliminate the problems of long experimental times and measurement difficulties.…”

“…Chen et al [19,20] analyzed the diffusion, permeation, and transfer behaviors of small molecules in dense polymer membranes using free volume and percolation theory. Lu et al [15] studied the diffusion of gas in amorphous polyisoprene and the relationship between the diffusion coefficient and temperature. Russell et al [2] compared the effect of carbon nanotubes (CNTs) and carbon black as fillers of fluorine rubber (FKM) on the various seal-related performance characteristics.…”

“…Lu et al. [15] studied the diffusion of gas in amorphous polyisoprene and the relationship between the diffusion coefficient and temperature. Russell et al.…”