Synthesis, Characterization, and CO(2)/N(2) Separation Performance of POEM-g-PAcAm Comb Copolymer Membranes

Alcohol-soluble comb copolymers were synthesized from rubbery poly(oxyethylene methacrylate) (POEM) and glassy polyacrylamide (PAcAm) via economical and facile free-radical polymerization. The synthesis of comb copolymers was confirmed by Fourier-transform infrared and proton nuclear magnetic resonance spectroscopic studies. The bicontinuous microphase-separated morphology and amorphous structure of comb copolymers were confirmed by wide-angle X-ray scattering, differential scanning calorimetry, and transmission electron microscopy. With increasing POEM content in the comb copolymer, both CO(2) permeability and CO(2)/N(2) selectivity gradually increased. A mechanically strong free-standing membrane was obtained at a POEM:PAcAm ratio of 70:30 wt%, in which the CO(2) permeability and CO(2)/N(2) selectivity reached 261.7 Barrer (1 Barrer = 10(−10) cm(3) (STP) cm cm(−2) s(−1) cmHg(−1)) and 44, respectively. These values are greater than those of commercially available Pebax and among the highest separation performances reported previously for alcohol-soluble, all-polymeric membranes without porous additives. The high performances were attributed to an effective CO(2)-philic pathway for the ethylene oxide group in the rubbery POEM segments and prevention of the N(2) permeability by glassy PAcAm chains.