Synthesis and Properties of Phthalonitrile Polymer with a Novel Piperazine Structural Curing Agent

A novel autocatalytic phthalonitrile (PN) monomer containing piperazine structure, namely 4‐[1‐(4‐aminophenyl)‐4‐(4‐phenyl)piperazine‐oxy]phthalonitrile (APPN), is synthesized from the nucleophilic substitution reaction of 1‐(4‐Aminophenyl)‐4‐(4‐hydroxyphenyl)piperazine and 4‐nitrophthalonitrile. The structure of the APPN monomer is characterized by Nuclear Magnetic Resonance (NMR) spectroscopy and Fourier Transform Infrared (FTIR) spectroscopy. The novel 4‐nitrophthalonitrile end‐capped compound APPN is firstly used to promote the curing reaction of PN monomer 1,3‐bis(3,4‐dicyanophenoxy)benzene (m‐BDB). Thermogravimetric Analysis (TGA) and Dynamic Mechanical Analysis (DMA) showed that the PN resin in the presence of 10 % of APPN possessed outstanding thermal and thermo‐oxidative stabilities as well as good mechanical properties, better than the properties of those with 20 % of APPN and 10 % of APPH. Its glass transition temperature ( T g ) is higher than 400 °C, and the polymer loses 5 % of its weight ( T 5% ) at 524 °C and shows a storage modulus of 1373 MPa at 400 °C.