Gas permeation properties of organic-inorganic hybrid membranes prepared from hydroxyl-terminated polyether and 3-isocyanatopropyltriethoxysilane

Organic-inorganic hybrid materials were prepared by reacting 3-isocyanatopropyltriethoxysilane (IPTS) with hydroxyl terminated poly(ethylene glycol) (PEG), poly(propylene glycol) (PPG) and poly(propylene glycol)-block-poly(ethylene glycol)-block-poly(propylene glycol) (PEPG), followed by hydrolysis and condensation with acid catalysis. Composite membranes have been obtained by casting hybrid sol on the microporous polysulfone substrate. The membranes were characterized by Fourier transform infrared (FT-IR), C-13 NMR and Si-29 NMR. The permeability coefficients of N-2, O-2, CH4 and CO2 were measured by variable volume method. The gas permeability coefficients increase with increasing molecular weight of the polyethers. For the membranes containing PEG and PEPG, the higher values of CO2 permeability coefficients and CO2/N-2 separation factors are due to the presence of ethylene oxide segments. In case of PEPG membranes, molecular weight has more influence on CO2 permeability than the effect of facilitation by ethylene oxide. The addition of TEOS into hybrid sol results in the decrease of all the gas permeability and does not affect the gas selectivity. PEG2000 membrane display the most performance among the hybrid membranes investigated here. The best values observed are CO2 permeability of 94.2 Barrer with selectivity of 38.3 for CO2/N-2 and 15.6 for CO2/CH4.