Studies on Polyimides Derived from Pyromellitic Dianhydride through Diels-Alder Polymerization

Novel polyimides containing thermoplastic and thermosetting merged segments in a chain have been developed via Diels-Alder intermolecular reaction of bisfuran A and bismaleimides B1-3. Thus, obtained intermediate Diels-Alder adducts C1-3 were aromatized and imidized (cyclized) through carboxylic and amide groups in the presence of acetic anhydride to afford polyimides D1-3. Bisfuran was prepared by condensation of pyromellitic dianhydride with furan-2-ylmethanamine and characterized by elemental, spectral and thermal technique. Synthesized Diels-Alder adducts and polyimides were characterized by elemental analysis, spectral features, number average molecular weight (Mn), degree of polymerization (DP) and thermal analysis. To facilitate the correct structural assessment and to be able to verify the occurrence of the polyimides, a model compound was prepared from phthalic anhydride and furan-2-ylmethanamine in a similar way. FTIR spectral features of polyimides D1-3 were compared with model compound and it was found to be quite identical. The in situ' glass fiber reinforced composites GFRC1-3 were prepared from the produced system and were characterized by chemical, mechanical and electrical analysis. All the composites depicted good mechanical and electrical properties and good resistance to organic solvents and mineral acids.