Separation performance of asymmetric membranes based on PEGDa/PEI semi-interpenetrating polymer network in pure and binary gas mixtures of CO2, N2 and CH4

Asymmetric membranes of semi-interpenetrating polymer networks (semi-IPN) were prepared with commercial poly (ether imide) (ULTEM®) and poly (ethylene glycol) diacrylate (PEGDa) in 1-methyl-2-pyrrolidinone (NMP). The selectivity and permeance of pure and mixed gases using carbon dioxide (CO2) feed concentrations of 10–40% in nitrogen (N2) or methane (CH4) were measured by the constant pressure and variable volume method at an absolute feed pressure of 1.35 MPa and 22 °C. The pure gas selectivity matched the mixed gas selectivity values at different feed concentrations, which indicated absence of plasticization. The fugacity based CO2/N2 selectivity of a semi-IPN with 6% PEGDa solids content reached 50 ± 4, which is comparable to the pure gas selectivity of a dense PEGDa film (α = 54) and is significantly higher than the dense film selectivity of PEI (α = 28). The selectivity for CO2/CH4 mixtures is 43 ± 10, comparable to the dense film properties of PEI (α = 39) and not the dense film selectivity of PEGDa (α = 20). The PEGDa/PEI semi-IPN membranes displayed synergistic properties, where the selectivity approached the higher value of the two materials used in making the semi-IPNs.