Syntheses of PEO Graft Copolyamides and the Permselectivity of CO₂

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Poly(ethylene oxide) graft copolyamides (PA-g-PEO and PA-g-PEOC) were prepared by a macromonomer method, and the effect of the PEO segment lengths or the polar end group of the graft copolymers on the CO₂ permselectivity was investigated. In addition, poly(ethylene oxide) and polydimethylsiloxane randomly graft copolyamide (PA-g-SEr) were prepared by a macromonomer method, and the effect of copolymer composition on the gas permeability was also investigated. The obtained polymers were soluble in aprotic polar solvents, such as DMF, NMP and DMSO. Then, the tough and flexible membranes could be prepared by solvent-casting method using NMP as solvent. The CO₂ permselectivity of the polymer membranes was evaluated. The CO₂ permeability coefficient of PA-g-PEO membrane containing the longer PEO segment was 32.6 Barrer, and the selectivity of CO₂/N₂ was nearly 50. It was also found that the moderate introduction of polydimethylsiloxane side chain was effective to increase the CO₂ permeability coefficient to 39.2 Barrer while maintaining the selectivity of CO₂/N₂. On the other hand, the introduction of the polar diethylcarbamoyl group into PEO chain end caused the decrease of the CO₂ permeability coefficient to 5.96 Barrer.