Study on thermal behaviors of a novel cruciform amide-containing phthalonitrile monomer

A novel cruciform amide-containing phthalonitrile monomer was synthesized from 4-(4′-aminophenoxy) phthalonitrile and 2,2′,5,5′-biphenyl tetraacyl chloride. Linear amide-containing phthalonitrile monomer was also prepared for comparison. Various spectroscopic techniques such as IR and 1H NMR confirmed the chemical structure of the monomers. X-ray powder diffraction analysis revealed the amorphous character of the cruciform monomer. Thermal behaviors of the monomers was investigated by rheology technique. Aromatic amide moiety played an important role in promoting the cure reaction of the phthalonitrile resins. Cruciform monomer displayed a larger processing window, relative to linear phthalonitrile monomer. The polymers derived from cruciform phthalonitrile monomer showed excellent thermal properties revealed by thermogravimetric analysis and differential scanning calorimetry. The IR spectra of the polymers confirmed that triazine formation may dominate the thermal polymerization reaction.