Gas Diffusion Analysis

Full-Atomistic Molecular Dynamics (FAMD) was used to evaluate the diffusivity of oxygen and carbon dioxide in PDMS and polyisoprene. For PDMS, this relates to the oxygen permeability of contact lenses; for polyisoprene, it relates to the gas barrier properties of tire materials. Differences in diffusivity due to temperature and molecular species were discussed.

Use Cases Highlights

Structure creation using scenario functionality
Evaluation of diffusion coefficients from molecular motion
Evaluation of differences in diffusivity due to molecular species and temperature

Structure creation using the scenario function

Construction of amorphous PDMS and PI structures with gas molecules inserted using J-OCTA’s scenario function is shown.

Oxygen molecules in PDMS

Evaluation of diffusion coefficient

From gas molecule dynamics results, the mean square displacement (MSD) was evaluated. From its slope, the self-diffusion coefficient was calculated. Comparing the self-diffusion coefficients of oxygen and carbon dioxide, trends consistent with experimental data were obtained. The temperature dependence of diffusion coefficients was also evaluated.

Temperature dependence of diffusion coefficient

Reference

[1] Jie Han and Richard H. Boyd, Polymer, vol. 37, 10, pp. 1797, 1996
[2] Extracts from Polyinfo Database
[3] Y. Tamai, H. Tanaka and K. Nakanishi, Macromolecules, vol. 27, pp. 4498, 1994

Details of analysis

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