Membrane Color and Gas Permeability of 6FDA-TeMPD Polyimide Membranes Prepared With Various Membrane Preparation Protocols

The relations among polyimide membrane colors, their gas transport and separation properties, and their fluorescence spectra were systematically investigated using fluorine-containing aromatic polyimide, 6FDA-TeMPD {[4,4-(hexafluoroisopropylidene) diphthalic anhydride] [(6FDA)-2,3,5,6-tetramethyl-1,4-phenylene-diamine (TeMPD)]}, which was used in electronic device and gas separation materials. Different molecular ordering structures of 6FDA-TeMPD polyimides were prepared by controlling kinds of casting solvents and dry conditions. This difference was based on the effect of charge transfer (CT) interaction formed by pi electrons of ring structures in polyimide. Membrane color measured using spectrophotometer determined colors as intrinsic parameters without sample collection. The permeability coefficients of oxygen and nitrogen of the 6FDA-TeMPD polyimide membranes were correlated with membrane color index parameters such as L*, a*, b*, and Delta E*, and fluorescence properties such as maximum peak emission wavelength lambda(max) and intensity I-max, which reflect molecular ordering affected by CT interaction in polyimide membranes. POLYM. ENG. SCI., 51:2360-2369, 2011. (C) 2011 Society of Plastics Engineers