Physical, optical and gas transport properties of new processable polyimides and poly(amideimide)s obtained from 4,4′-[oxybis(4,1-phenylenethio)]dianiline and aromatic dianhydrides

Aromatic diamine 4,4'-[oxybis(4,1-phenylenethio)]dianiline and various dianhydrides with isopropylidene, hexafluoroisopropylidene, fluorenylidene diphenyl, ether, thioether and/or amide linkages were applied in a polycondensation reaction to obtain new processable polyimides and poly(amideimide)s (PIs). PIs were synthesized by the conventional two-step procedure of ring-opening polyaddition and subsequent thermal cyclic dehydration. The structures of the polymers were characterized with Fourier-transform infrared spectroscopy and elemental analysis. The thermal behaviors of the PIs were characterized with differential scanning calorimetry, thermogravimetric analysis and dynamic mechanical thermal analysis. The glass transition temperature (T-g) of the PIs were in the range of 175-298 degrees C and depended on the dianhydride used. The 5% weight loss temperatures were in the range of 423-515 degrees C, which shows the high thermal resistance characteristics of the PI. The optical absorption properties in the UV-visible range of the obtained polymers were studied in solution and in the solid state. The average refractive indices (n) of the PI films measured at the low absorption range were in the range of 1.96-1.50. The permeation properties of the PIs were studied for He, O-2, N-2 and CO2 at 6 atm, with a constant pressure/variable volume setup. The hexafluoroisopropylidene-based PI showed the largest permeability for all gases. Polymer Journal (2011) 43, 621-629; doi:10.1038/pj.2011.28; published online 20 April 2011