A diamine containing a pendant phenoxy group, 1-phenoxy-2,4-diaminobenzene, was synthesized and condensed with different aromatic dianhydrides [4,4 0 -oxydiphthalic dianhydride, 4,4 0 -(hexafluoroisopropylidene)diphthalic anhydride, 3,3 0 ,4,4 0 -benzophenone tetracarboxylic dianhydride, 3,3 0 ,4,4 0 -biphenyltetracorboxylic dianhydride, and pyromellitic dianhydride] by one-step synthesis at a high temperature in m-cresol to obtain polyimides in high yields. Most of the polyimides exhibited good solvent solubility and could be readily dissolved in chloroform, sym-tetrachloroethane, N,N-dimethylformamide, N,N-dimethylacetamide, and nitrobenzene. Their inherent viscosities were in the range of 0.33-1.16 dL/g. Wide-angle X-ray spectra revealed that these polymers were amorphous in nature. All these polyimides were thermally stable, having initial decomposition temperatures above 5008C and glass-transition temperatures in the range of 248-2818C. The gas permeability of 4,4 0 -oxydiphthalic dianhydride and 4,4 0 -(hexafluoroisopropylidene)diphthalic anhydride based polyimides was investigated with pure gases: He, H 2 , O 2 , Ar, N 2 , CH 4 , and CO 2 . A polyimide containing a À ÀC(CF 3 ) 2 À À linkage showed a good combination of permeability and selectivity.
