Integrated Simulation System for Soft Materials.

The permeability of small(gas) molecule in polymer matrix is extremely important in the manufacturing of such products as film and contact lenses. The simulation of the small molecule's permeability for these types of polymers has recently been drawing much attention.

By using COGNAC, molecular dynamics simulator, small molecule's diffusion properties in the amorphous polymer (diffusion coefficient) is possible to evaluate.

Evaluation of Diffusion Coefficient of Oxygen in Polydimethylsiloxane (PDMS) (Reference [3])

The diffusion coefficient has been calculated for oxygen molecules in the PDMS which is used as material for contact lenses and other similar items. For comparison, the diffusion coefficient of carbon dioxide has also been calculated.

In this simulation we have succeeded in obtaining the calculated values close to the experimental values. These MD diffusion coefficient estimations are used more as a tool to postulate changes in diffusion behavior after making changes to diffusion molecules or polymer matrices. The quantitative values of the result are not of so much importance. In this case, the diffusion coefficient of oxygen is higher than that of carbon dioxide, which matches experimental data. MD calculations are coincident with the experimental data qualitatively.

Evaluation of Diffusion Coefficients for Carbon Dioxide and Oxygen Molecules in Cis-1,4-Polyisoprene

The diffusion coefficient has been calculated for carbon dioxide and oxygen molecules in cis-1,4-polyisoprene, which is often used in rubber material. The results of carbon dioxide are nearly coincident with the experimental data. The oxygen results are just a bit high, but the overall relationship between the diffusion coefficients of carbon dioxide and oxygen are coincident with experimental data.

Evaluation of Diffusion Coefficients of Methane in Polyisoprolene

Here we evaluate the temperature dependency of diffusion coefficients. The X- axis is 1000/T (T being temperature), and the Y-axis is the log of the diffusion coefficient (log D). The result shows a linear relationship. This calculation result is a near-perfect reproduction of the results found in the reference[1].