Interfacial layer thickness is a key parameter in determining the gas separation properties of spherical nanoparticles-mixed matrix membranes: A modeling perspective

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• A new model is proposed for prediction of gas permeability of SP-MMMs. • The model is developed based on an analogy between heat transfer and mass transfer. • The model is able to quantify the role of SP/matrix interface in gas permeability. • Dense interfacial layer thickness is independent of nature of gas molecules. • Dense interfacial layer thickness is correlated to the interfacial interactions. The existing traditional models cannot accurately predict the gas permeability of spherical nanoparticle-mixed matrix membranes (SP-MMMs) due to ignoring the physical and chemical characteristics of the SP/matrix interface. In this paper, first, a new model is derived for the prediction of thermal conductivity of SP-polymer composites according to multiple scattering theory. Then, a new theoretical model for gas permeability of SP-MMMs is developed based on the analogy with the derived model for the prediction of thermal conductivity. The significant feature of the new model is its ability to quantify the crucial role of SPs/matrix interface in gas permeability by introducing a new dense interfacial layer thickness ( a int ) parameter, which increases with increasing the strength of interfacial interactions. It is demonstrated that the value of a int is independent of the nature of gas molecules and mathematically correlated to the strength of SPs/matrix interfacial interactions. Finally, the gas permeability of SP-MMMs is accurately predicted by inserting the values of non-adjustable a int parameter, obtained from the correlation, diameter of SPs as well as the gas permeability of matrix into the new model, without using any adjustable parameter. Moreover, this technique can be utilized to determine the dense interfacial layer thickness in SP-polymer composites using gas permeation data.