Synthesis, curing kinetics and thermal properties of a novel self-promoted fluorene-based bisphthalonitrile monomer

Abstract

A novel amino-containing fluorene-based bisphthalonitrile monomer, 9,9-bis(4-aminophenyl)-2,7-(3,4-dicyanophenoxy)-fluorene (AFPN), was successfully synthesized via the nucleophilic displacement of the nitro-substituent from 4-nitrophthalonitrile. The structure of AFPN was confirmed by Fourier transform infrared (FT-IR), 1H and 13C nuclear magnetic resonance (NMR). Its curing behavior and curing kinetics were investigated using differential scanning calorimetry (DSC) and FT-IR techniques. Isoconversional method based on Starink was applied to analyze the curing process of AFPN. The thermal and mechanical properties of the cured product were evaluated by thermogravimetric analysis (TGA) and dynamic mechanical analysis (DMA). The AFPN showed a self-promoted curing behavior, whereas the introduction of the amino groups increased its curing rate and lowered its curing temperature. Additionally, its cured polymer showed an excellent thermal and thermo-oxidative stability, since its char yield reached 76.5% at 800°C in nitrogen and 83.4% at 600°C in air, respectively.