POLYIMIDES CONTAINING NONAROMATIC NITROGEN LINKAGES

Two diamines, 2,5-bis(4-aminophenyl)-2,5-diazahexane and 1,4-bis(4-aminophenyl)-1,4-diazacyclohexane were chosen as components for polyimidizations because they have melting points that differ by nearly 200-degrees-C (66-67 and 229-230-degrees-C, respectively) and are relatives of p-nitro-N,N-dimethylaniline. The melting points of the model compounds (phthalic anhydride) do not differ by as much as those of the free amines [303-304 and 386-degrees-C (DSC), respectively]. Six polyimides were prepared by a two-step polycondensation of the diamines with pyromellitic dianhydride, benzophenonetetracarboxylic dianhydride, and 5,5'-[2,2,2-trifluoro-1-(trifluoromethyl)ethylidene]bis-1,3-isobenzofurandione. DSC thermograms failed to indicate any distinct transitions up to 450-degrees-C, however, the polyimide prepared from 2,5-bis(4-aminophenyl)-2,5-diazahexane and pyromellitic dianhydride shows a slight break in its DSC curve at 233-degrees-C.