ABSTRACT
ROHITKUMAR H. VORA* Advanced Polymer Research & Technologies, 505 Cinder Road, Edison, NJ 08820, USA
Abstract-Development of high-performance polymer/inorganic clay nanocomposite (i.e., Ceramer) technology is an ongoing research effort at various academic and industrial organizations. In our effort to develop aromatic-polyimide-chemistry-based advanced high-performance polyimide/inorganic clay nanocomposites (termed as ‘CeramImide’ materials) technology, 1,2’-bis(4aminophenoxy) benzene (o-BAPOB) and 4,4’-bis(4-aminophenoxy) diphenyl sulfone (p-SED) and partially fluorinated dianhydride 2,2’-bis(3,4-dicarboxyphenyl) hexafluoropropane dianhydride (6FDA)-based series of designed fluoro-poly(ether amic acid)s (6F-PEAA) and their (6FPEAA)/organo-soluble montmorillonite (MMT) clay nanocomposite pre-formulations containing varying percentages of diamine modified (ion-exchanged) organo-soluble MMT clay were synthesized. Self-supporting films of fluoro-poly(ether imide) (6F-PEI)/organo-soluble MMT clay CeramImide material were obtained from (6F-PEAA)/organo-soluble MMT clay nanocomposite preformulations by casting their thin films on glass plates and thermally curing at pre-programmed elevated temperatures. The exfoliation of organo-soluble MMT clay at molecular level in the nanocomposites was confirmed by XRD analysis. A modified and expanded mathematical relation termed as the Fox-Vora equation, was derived for the calculation of precise molar concentrations of monomers for the designed architecture of a co-polyimide having a pre-selected glass-transition temperature (Tg). Long-term thermo-oxidative stability (TOS), activation energy of thermal degradation kinetics, moisture absorption at elevated temperature, chemical resistance, mechanical behavior, and surface properties of these designed CeramImide material films were systematically studied. The dielectric constants (ε′) of these polyimides and fluoro-co-polyimides experimentally determined at 1 kHz frequency at 25°C were found to be in good agreement with the values estimated using the Lorentz-Lorenz, Vogel and Vora-Wang equations. The results of this extensive research are summarized and discussed.
