In industrial processes membranes made of composite polymer material are widely employed to separate gas mixtures.  These membranes have better performance than membranes consisting of polymer alone.  To understand the mechanism and therefore aid membrane design it is essential to explore the penetrant transport in these materials from the molecular level.  In this paper, we consider molecular dynamics (MD) simulations for the molecular level studies.  The complicated structure of the composite PMP and silica nanoparticle was modeled first and subsequently relaxed successfully.  Using the relaxed structure, we established the variation of the cavity size distribution in the presence of the silica nanoparticle.  The diffusivity of different penetrants, including H2, O2, Ar, CH4 and n-C4H10 was determined through least squares fit of the data of mean square displacement at different times during the production run.  The square of the correlation coefficient was employed to determine if the diffusion took place in the Fickian diffusive regime.  Based on the resistance concept in heat and mass transport, we successfully formulated an expression to correlate the diffusivities of the same penetrants in a different matrix.  Finally, the solubility coefficients and the permeability of different penetrants in PMP and the composite were calculated.

Molecular dynamics simulation of penetrants transport in membranes constructed from composite poly (4-methyl-2-pentyne) and silica nanoparticles

243rd National Meeting (2012)

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