Synthesis and characterization of metal-containing sulfonated polyimide membranes and their gas separation properties

We studied the synthesis and characterization of a thermally stable metal-containing in sulfonated polyimides (M-SPI) based on benzophenone tetracarboxylic dianhydride (BTDA), 4, 4’-diamino 2, 2’-biphenyl disulfonic acid (BDSA) and meta-phenylenediamine (mPDA). X-ray photoelectron spectroscopy (XPS) was chosen as a tool for confirmation of metal substitution in sulfonic acid group. Thermogravimetric analysis (TGA) spectrum of the M-SPI showed approximately 5% weight loss in the range of 250–350ºC and the final decomposition began at around 500ºC. Wide angle X-ray diffraction (WAXD) spectra of M-SPI show no crystalline behavior, indicating an amorphous structure of the polymer. The water sorption of the M-SPI was investigated at 25ºC and 60% RH. The diffusion coefficient and water uptake were estimated to be 2.68×10–7 cm2/s and 2.33 wt% for NaSPI 1091 and 3.79×10–7 cm2/s and 4.03 wt% for Na-SPI 1082.