Synthesis of high performance phenolphthalein-based cardo poly(ether ketone imide)s via aromatic nucleophilic substitution polymerization

Abstract

A series of cardo poly(ether ketone imide)s (PEKI-C) containing large-volume bulky phthalide groups were prepared by aromatic nucleophilic substitution reaction of commercially available phenolphthalein and 4,4′-bis(4-fluorophthalimido)diphenyl ether/4,4′-difluorobenzophenone. The glass transition temperatures (Tgs) increased from 221 to 278 °C with increasing the content of 4,4′-bis(4-fluorophthalimido)diphenyl ether moiety in the copolymerization. The 5% weight loss temperatures (T5%) of PEKI-C (a–e) reached up to 472–495 °C in nitrogen and 466–481 °C in air. Flexible films, which could be easily cast from the polymer solutions, exhibited good mechanical properties with tensile strengths of 73–124 MPa, elongations at break of 9.7–12.8%, and tensile moduli of 2.2–2.8 GPa. Their films with cut-off wavelengths from 336 to 368 nm were transparent and essentially colorless. It is noted that the Tg, T5%, tensile strengths, elongations at break, and tensile moduli of PEKI-C (a–e) increased with increasing the content of 4,4′-bis(4-fluorophthalimido)diphenyl ether in the copolymerization.