Synthesis of room temperature ionic liquids based random copolyimides for gas separation applications

Random copolyimides were synthesized using diamino functional room temperature ionic liquid (RTIL) and were characterized. Specifically, a diamino functional RTIL, 1,12-di[3-(3-aminopropyl) imidazolium] dodecane bis[(trifluoromethyl)sulfonyl] imide ([C12(DAPIM)2][Tf2N]2), was reacted with 2,2-bis(3,4-carboxylyphenyl) hexafluoropropane dianhydride (6FDA) and m-phenylenediamine (MDA) to form random cooplyimides with a [C12(DAPIM)2][NTf2]2 concentration varying from 10 to 30 mol%. Incorporation of [C12(DAPIM)2][NTf2]2 within the 6FDA–MDA backbone resulted in decreases in the polymer thermal stability, glass transition temperature, d-spacing, fractional free volume and increments in density. The gas permeability, solubility and diffusivity of the random copolyimides decreased and the permeability selectivities increased compared with the pure 6FDA–MDA polyimide.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Synthesized 6FDA–(MDA/RTIL) random copolyimides. ► Tested gas transport properties of all copolyimides. ► Gas sorption isotherms were monitored. ► Adding RTILs increased selectivity but decreased permeability.