Gas permeabilities of cellulose nitrate/poly(ethylene glycol) blend membranes

Abstract The permeability (P) of cellulose nitrate (CN)/poly(ethylene glycol) (PEG) blend membranes for N2, O2, and CO2 has been measured as a function of film composition. The system CN/PEG‐300 showed excellent miscibility, and films of the composition from 100/0 to 50/50 could be used for permeability measurements. P for each gas has been found to be almost constant or rather slightly lowered up to ca. 20 wt % PEG‐300 content and then increased appreciably with increasing fraction of PEG. The increment of permeability was most remarkable for CO2, and hence the permselectivity for CO2 was considerably enhanced. Such a behavior of P has been found to be attributable to the plasticizing effect of PEG molecule lowering the glass transition temperature of the blend polymers. The effect of the molecular weight of PEG and that of closed voids generated in glassy blend membranes fabricated from acetone cast on gas permeabilities have been also discussed.