Thermal cross-link between 2,5-furandicarboxylic acid-based polyimides and bismaleimide via Diels–Alder reaction

A series of cross-linked polyimides (PIs) were prepared via two-step solution polycondensation from 2,2-bis[4-(3,4-dicarboxyphenoxy)phenyl]propane dianhydride (BPADA) and 2,5-furandicarboxylic acid-based diamines, N,N ′-bis(4-amino-2-(trifluoromethyl)phenyl)furan-2,5-dicarboxamide (TFFDA) and N,N ′-bis(4-aminophenyl)furan-2,5-dicarboxamide ( p -FDDA), followed by thermal crosslinking reaction with bismaleimide. The thermal crosslinking reaction and its mechanism were studied by FTIR spectra and model reaction analysis, which showed Diels–Alder reaction between furan group and maleimide group played a main role in the thermal treatment. The properties of cross-linked PIs were characterized using dynamic mechanical thermal analysis, thermogravimetric analyses, tensile testing, ultraviolet-visible spectra, and wide-angle X-ray diffraction. The cross-linked polyimide film showed improved solvent-resistance, thermal and mechanical properties with T g values of 234–306 o C, tensile strengths of 82–98 MPa and moduli of 2.3–3.0 GPa. Graphical Several cross-linked polyimides (PIs) were prepared via polycondensation of dianhydride and 2,5-furandicarboxylic acid (2,5-FDCA)-based diamines, N,N ′-bis(4-amino-2-(trifluoromethyl)phenyl)furan-2,5-dicarboxamide, and N,N ′-bis(4-aminophenyl)furan-2,5-dicarboxamide, and following thermal crosslinking reaction with bismaleimide. These PIs exhibit outstanding thermal and mechanical properties. The crosslinking network of 2,5-FDCA-based PIs and bismaleimide is constructed for the first time by Diels–Alder reaction. The thermal crosslinking mechanism is also studied in detail using model reaction.