Synthesis and characterization of hyperbranched poly(aryl ether ketone) terminated with phthalonitrile group

Abstract

A series of novel cross-linkable hyperbranched poly(aryl ether ketone) (HPAEK) polymers (CN-HPAEK n) were synthesized using 2,4′,6-trifluoro-benzophenone as a BB′2 monomer, hydroquinone as an A2 monomer, and 4-nitrophthalonitrile as an endcapping reagent and characterized by Fourier transform infrared spectroscopy and proton nuclear magnetic resonance. The average molecular weights of the prepared polymers were determined by gel permeation chromatographic analysis. Thermal cross-linking of CN-HPAEK n, catalyzed by p-bis[4-(4-aminophenoxy)phenyl]sulfone, was then performed via heating their films up to 350°C. The uncured synthesized polymers had good solubility, while the cured samples became insoluble in common organic solvents. Spectra measurement demonstrated trimerization reaction of terminal cyano groups to form triazine rings. The resulting cured samples had high glass transition temperatures and excellent thermal stability with high char yield. Gel content measurements demonstrated that the cured polymers had high cross-linking density, with significantly high gel content of over 95.0%. Thermal mechanical analysis indicated that the cured phthalonitrile resins possessed good thermal mechanical properties at elevated temperatures. These kinds of phthalonitrile resins may be used as a candidate for high-performance polymeric film materials.