Thermal degradation behaviors of poly (arylene ether nitrile) bearing pendant carboxyl groups

Abstract Poly (arylene ether nitrile) (PAEN) bearing pendant carboxyl groups integrates the outstanding performances of special thermoplastics with the merit of solubility and has been extensively employed to prepare advanced composites for uses in dielectric and fluorescence field. This study firstly reported the thermal pyrolysis behavior of diphenolic acid (DBA)-based PAEN characterized by TG/DTG, TG-FTIR and TG-MS technique under non-oxidizing gaseous environment. It is found that PAEN showed third-order degradation mechanism: (i) Side chain degradation starts at 350–480 °C in the pentanoic acid moiety and CN groups, resulting in the main pyrolysis products of Ph-CH2-Ph-O-Ph or Ph-Ph-O-Ph by releasing CH4, H2O, HCN, CO, HCHO, CH3OH, CO2, HCOOH, C4H8. (ii) Main chain pyrolysis was caused by cleavages of C C and C O bond in backbone at 480–650 °C, mainly releasing aromatic compounds including C6H6, C7H8, C6H5OH, C6H5OCH3, etc. (iii) Carbonization happened over 650 °C and finally formed an extended aromatic array of graphite. The obtained results not only help our understanding for the identification, structural determination, and thermal resistance of PAEN materials, but also will guide molecular design of poly arylene ethers with higher thermal durability.