Synthesis and characterization of new fluorene‐based poly(ether imide)s

A novel bis(ether anhydride) monomer, 9,9-bis[4-(3,4-dicarboxyphenoxy)phenyl]fluorene dianhydride (4), was synthesized from the nitrodisplacement of 4-nitrophthalonitrile by the bisphenoxide ion of 9,9-bis(4-hydroxyphenyl)fluorene (1), followed by alkaline hydrolysis of the intermediate tetranitrile and dehydration of the resulting tetracarboxylic acid. A series of poly(ether imide)s bearing the fluorenylidene group were prepared from the bis(ether anhydride) 4 with various aromatic diamines 5a–i via a conventional two-stage process that included ring-opening polyaddition to form the poly(amic acid)s 6a–i followed by thermal cyclodehydration to the polyimides 7a–i. The intermediate poly(amic acid)s had inherent viscosities in the range of 0.39–1.57 dL/g and afforded flexible and tough films by solution-casting. Except for those derived from p-phenylenediamine, m-phenylenediamine, and benzidine, all other poly(amic acid) films could be thermally transformed into flexible and tough polyimide films. The glass transition temperatures (Tg) of these poly(ether imide)s were recorded between 238–306°C with the help of differential scanning calorimetry (DSC), and the softening temperatures (Ts) determined by thermomechanical analysis (TMA) stayed in the range of 231–301°C. Decomposition temperatures for 10% weight loss all occurred above 540°C in an air or a nitrogen atmosphere. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 1403–1412, 1999