Synthesis, characterization, and properties of novel diol monomers and processable thermally stable polyimides

Abstract

Diimide-diol monomers containing aliphatic spacer N,N′-bis (2-hydroxyethyl) biphenyl tetracarboxylic diimide and N,N′-bis(2-hydroxyethyl)benzophenone tetracarboxylic diimide were synthesized by a nucleophilic substitution reaction that involved ethanolamine and commercially available aromatic dianhydrides. The structures of the monomers were characterized by FT-IR and 1H-NMR. Processable polyimides (PIs) containing aliphatic spacer were synthesized from these new diols and 4,4′-dichlorodiphenyl sulfone/4,4′-difluorobenzophenone by nucleophilic substitution reaction. The polyimides were characterized by FT-IR, 1H-NMR, X-ray diffraction (XRD), thermogravimetry (TG), differential scanning calorimetry (DSC), solution viscosity, and solubility test. The X-ray diffraction patterns indicated that all these polyimides were amorphous and soluble in common organic solvents. Thermogravimetry analysis indicated that the polyimides exhibit good thermal stability, and 10 % weight loss occurred in the temperature range 375 to 429 °C. The limited oxygen index (LOI) values of polyimides were in the range 36.3 to 37.5 and such PIs can be used as self extinguishing polymers.