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Enhanced gas permeability by fabricating mixed matrix membranes of functionalized multiwalled carbon nanotubes and polymers of intrinsic microporosity (PIM)

Khan, Muntazim M., Filiz, Volkan, Bengtson, Gisela, Shishatskiy, Sergey, Rahman, Md.Mushfequr, Lillepaerg, Jelena, Abetz, Volker
Journal of membrane science 2013 v.436 pp. 109-120
artificial membranes, carbon dioxide, carbon nanotubes, diffusivity, mechanical properties, nitrogen, permeability, polyethylene glycol, scanning electron microscopy, solubility, sorption isotherms, thermogravimetry
In this study, mixed matrix membranes (MMM) consisting of multi-walled carbon nanotubes (MWCNTs) embedded in PIM-1 matrix have been fabricated via solution casting method and their gas transport properties are investigated. The MWCNTs were chemically functionalized with polyethylene glycol (PEG) for a better dispersion in the polymer matrix. The effect of functionalized MWCNTs (f-MWCNTs) loading on gas permeation properties of the MMM were investigated by varying the MWCNTs loading in a PIM-1 matrix from 0.5 to 3.0wt%. The derived MMM were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and single gas permeation tests. Gas permeation measurements showed that MMM incorporated with modified and non-modified CNTs exhibited different gas separation performance. The f-MWCNT MMM show better performance compared to MMM with non-modified CNTs in terms of dispersion and permeability at 2wt% f-MWCNTs loading without sacrificing selectivity. According to diffusivity and solubility data derived from the time-lag method, the PEG chains on MWCNTs show interaction with CO₂ as indicated by an increase of the solubility of the polar gas and a reduction of the solubility of non-polar gas, which is advantageous for CO₂/N₂ separation. The mechanical properties and experimental sorption isotherms of CO₂ and N₂ of the f-MWCNTs/PIM MMM were enhanced as well.