Synthesis and gas transport properties of polyamide membranes containing PDMS groups

A series of gas-separation polyamide-poly(dimethylsiloxane) (PA-PDMS) membranes containing PDMS groups were synthesized through the polycondensation reaction. The structural characteristics of polymers were evaluated by ¹H-NMR spectroscopy (NMR), Fourier-transform infrared spectroscopy (FTIR) and UV-vis absorption spectroscopy. The permeability and selectivity behavior was studied at different temperatures (25-55 °C) and pressures (1.0-3.0 atm), using various gases, such as H₂, O₂, CO₂, CH₄, and N₂. The effect of chemical structure, PDMS content, operating pressure and temperature on gas permeability was explored and discussed. Gas-permeation measurements showed that polyamides containing PDMS groups exhibited different separation performance. The PA-PDMS-20 membrane with 20 wt% PDMS exhibited the highest selectivity (CO₂/N₂ = 41.84 and O₂/N₂ = 7.01) at 35 °C and 3.0 atm while CO₂ and O₂ permeability was 29.29 barrer and 4.91 barrer, respectively.