SYNTHESIS AND CHARACTERIZATION OF POLYIMIDES BASED ON NEW FLUORINATED3,3'-DIAMINOBIPHENYLS

Two new fluorinated diamine monomers, 3,3'-diamino-5,5'-bis(trifluorom ethyl) biphenyl and 3,3'-diamino-6,6'-bis(trifluoromethoxy) biphenyl, as well as a known nonfluorinated analog, 3,3'-diaminobiphenyl, were s ynthesized. Reaction of these diamines with rigid, highly rod-like dia nhydrides produced poly(amic acid)s and polyimides, which were spin co ated and thermally treated to produce polyimide films for evaluation i n electronics applications. It was hoped that these polyimide films wo uld exhibit an ideal combination of low thermal expansion, reduced wat er absorption, and low dielectric constant but with improved elongatio n due to the ''crankshaft'' nature of the 3,3'-biphenyl unit. Unlike p olyimide films from analogous 4,4'-diaminobiphenyls, however, the 3,3' -diaminobiphenyl-based polyimides did not yield low in-plane thermal e xpansion coefficient in spin-coated films. In some cases high elongati on was achieved, but with high thermal expansion. These new diamines m ay nevertheless find utility in polyimides and polyaramides for membra ne, fiber, and other applications. Additionally, they may be useful in modifying the properties of polymer backbones via copolymerization. ( C) 1997 John Wiley & Sons, Inc.