Melt-Polymerizable Bisimido-Bisphthalonitriles Containing Silicon, Fluoro, and Ether Groups: Synthesis, Characterization, and NMR Study

Various melt-polymerizable bisimido-bisphthalonitrile polymer precursors were synthesized by the reaction of 4-aminophthalonitrile (4-APN) with bis(3,4-dicarboxyphenyl)dimethylsilane dianhydride (SIDA), 4,4'-hexafluoroisopropylidene diphthalic anhydride (6FDA), bis (3,4-dicarboxyphenyl)ether dianhydride (ODPA), and 3,3', 4,4'-tetracarboxylicbenzophenone dianhydride (BTDA) in an aprotic solvent. The synthesized monomers showed crystalline melting at 269 and 271 deg C. Elemental analysis, differential thermal analysis (DTA), infrared (IR), nuclear magnetic resonance ( exp 1 H-NMR) and mass spectral studies were carried out to characterize the synthesized monomers Thermogravimetric analysis (TGA) of the synthesized monomers showed their thermal stability at 410-400 deg C. A detailed study and NMR investigation of the first step of condensation reaction was carried out and indicated the formation of a transient charge transfer complex. Thermal cyclization of the formed intermediate, however, gave the required monomers. A preliminary study demonstrated that melt-polymerization of the synthesized monomers gave thermally-stable, tough polymers.