Characterization of Composition-Dependent Maxwell-Stefan Diffusivities in Mixtures of Polydimethylsiloxane, Nerve Agent VX, and Methanol

SA Bringuier and MJ Varady and TP Pearl and BA Mantooth, INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH, 56, 3713-3725 (2017).

DOI: 10.1021/acs.iecr.7b00159

The composition-dependent self- and Maxwell-Stefan (MS) diffusivities of binary and ternary mixtures consisting of polydimethylsiloxane (PDMS), nerve agent O-ethyl S-2(diisopropylamino) ethyl methylphosphonothioate (VX), and methanol are investigated using equilibrium molecular dynamics (MD) simulations. The intention of these simulations is to provide insight into mass transport characteristics that are crucial in the decontamination of hazardous chemicals absorbed in polymeric materials. We find that in some mixtures the self-diffusivities have appreciable composition dependence. In the case of the MS diffusivities, we have compared the MD-calculated quantities to the Darken and Vignes models for composition-dependent MS diffusivities. We observe that in binary and ternary mixtures the MS diffusivities display composition dependence and in some cases agree with the models. The composition dependence is analyzed, in terms of structural changes for dilute and concentrated mixtures, and we observe that associative interactions between molecules appear to impact composition dependence.

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