Fabrication and Characterization of polyimide mixed matrix membranes containing functionalized MWCNTs by beta-cyclodextrin

In this paper, synthesized (raw) multi-walled carbon nanotubes (MWCNTs) were functionalized with beta-cyclodextrin (bC) using Chen’s soft cutting technique. Raw multi-walled carbon nanotubes (r-MWCNTs) and functionalized multi-walled carbon nanotubes (f-MWCNTs) were characterized by transmission electron microscope (TEM). Mixed matrix membranes (MMMs) were fabricated using the phase inversion method and were characterized by permeation tests using methane and carbon dioxide as test gases. The TEM results showed that beta-cyclodextrin; as a soft cutting or functionalization agent; can attach to the outer surface of the nanotubes and wrap them axially. Permeation tests showed that addition of 2 wt. % functionalized MWCNTs into the casting dope increases CO2/CH4 ideal selectivity from 24.13 to 38.88. In addition, the glass transition temperature of MMMs containing 2 wt. % f-MWCNTs was 320.58 o C while the glass transition temperature of the neat polyimide membrane was 312.12 oC. The increase in the glass transition temperature was attributed to the good dispersion of the functionalized MWCNTs inside the polymer matrix.