Poly(vinylalcohol)/poly(ethyleneglycol)/poly(ethyleneimine) blend membranes - structure and CO2 facilitated transport

Poly(vinylalcohol) (PVA)/poly(ethyleneimine) (PEI)/poly(ethyleneglycol) (PEG) blend membranes were prepared by solution casting followed by solvent evaporation. The effects of the blend polymer composition on the membrane structure and CO2/N2 permeation characteristics were investigated. IR spectroscopy evidenced strong hydrogen bonding interactions between amorphous PVA and PEI, and weaker interactions between PVA and PEG. DSC studies showed that PVA crystallization was partially inhibited by the interactions between amorphous PVA and PEI blend, in which PEG separated into nodules. The CO2 permeability decreased with an increase in CO2 partial pressure in feed gas, while the N2 permeability remained constant. This result indicated that only CO2 was transported by the facilitated transport mechanism. The CO2 and N2 permeabilities increased monotonically with the PEI content in the blend membranes, whereas the ideal selectivity of CO2 to N2 transport showed a maximum. When CO2 is humidified, its permeability through the blend membranes is much higher than that of dry CO2, but the change in permeability due to the presence of humidity is reversible.