Polymeric membrane based-gas separation has drawn great attention for a range of molecular separations over competing technologies. For any gas separation membrane it is desirable to have good selectivity for one gas over another, combined with high permeability. Aromatic polyimides can be used as membrane materials because of their outstanding set of physical properties. In this context, a series of poly(ether imide)s (PEI)s has been synthesized from the reaction of benzyl ether substituted, fluorinated diamine monomer, 4,4'-((2',5'-bis(benzyloxy)-3,3''-bis(trifluoromethyl)-[1,1':4,4''-terphenyl]-4,4''-diyl)bis(oxy))dianiline (TADBE) with different fluorinated and non-fluorinated aromatic dianhydrides. The membranes were prepared directly by the thermal imidization of the poly(amic acid)s following a programmed heating up to 250 oC. The polymers were well characterized by different analytical techniques. Synthesized polymers have drawn much attention because of their superior mechanical strength, thermal properties, organo-solubility. The membranes were transparent and flexible and the PEIs were readily dissolved in numerous organic solvents and cast into freestanding flexible films with tensile strength up to 159 MPa and elongation at break up to 106 %. The films showed dielectric constant as low as 2.47 at 1MHz and 30 oC. The polymers showed 10% weight loss temperature above 440 °C in air with high Tg values (as high as 252 oC) under nitrogen. The structure-property correlations on gas transport properties and chemical structure and different physical properties of these PIEs were established. The best combination of selectivity and gas permeability value is seen for the polymer with 6FDA fragment (PEI-b). The group contribution method predicts the permeability coefficients exceptionally well in all three PEIs and for different gases. Whereas, molecular dynamics simulations provide a better insight on free volume: size, shape, connectivity and morphology of the PEIs.

Semi-fluorinated poly(ether imide)s with benzyl ether moiety: Synthesis, characterization, gas permeation study and molecular dynamics simulations

ACS Spring Meeting 2021

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