Synthesis and thermal properties of bisphthalonitriles containing aromatic ether nitrile linkages

Low-melting bisphthalonitrile oligomers with variable length of aromatic ether nitrile linkages (nPEN-BAPh) was firstly synthesized and the length of the linkages (n) was controlled by mole ratio of 2, 6-dichlorobenzonitrile and bisphenol A. The oligomers were characterized by FTIR and NMR spectra, and detailed study showed that the linkages were constructed in the backbone of nPEN-BAPh. The FTIR showed, with the curing reaction progressed, the characteristic peak of nitrile at 2230 cm⁻¹ disappeared while the characteristic peak of phthalocyanine ring at 3290, 1010 cm⁻¹ and triazine ring at 1360 cm⁻¹ appeared. The melting and polymerization temperature of the oligomers was around 60 °C and 220 °C, respectively. So a large processing window was obtained. The char yields of completely cured materials were above 65% at 800 °C in nitrogen and over 70% at 600 °C in air. All materials exhibited excellent thermal and thermo-oxidative stability.