Synthesis, characterization and studies of properties of six polyimides derived from two new aromatic diamines containing a central silicon atom

Two series of novel aromatic polyimides (PIs) containing three polymers each one were prepared using two new aromatic silylated-diamine monomers. These monomeric diamines contain biphenylsilane units and biphenyl moieties in their structures. All PIs were obtained in high yield and the inherent viscosities were in the range of 0.44 to 0.82 dL/g. Polyimides showed excellent solubility in a wide variety of aprotic polar solvents, including THF and chloroform and were thermally stable with thermal decomposition temperature (TDT_10%) over 500 °C and high glass transition temperatures (Tg) between 230 and 270 °C. Additionally, two films were prepared and gas transport properties were determined. These films offered a reasonably acceptable balance of permeability and selectivity with values close to a commercial polyimide (Matrimid), in particular for the CO₂/N₂ gases pair. Experimental density of the films was measured and the fractional free volume was calculated.