Linear Poly(arylene ether)s with Pendant Benzoyl Groups: Geometric Isomers of PEEK or Substituted Poly(phenylene oxide)?

Abstract

The characterization and nucleophilic aromatic substitution (NAS) behavior of 3,5-difluorobenzophenone, 5, are reported. The reactivity of the electrophilic sites, activated by only a benzoyl group located in the meta position, in 5 was probed via NMR spectroscopy and model reactions and was determined to be sufficient to undergo typical NAS reactions. Displacement of the first fluoride atom in 5, with the phenoxide ion derived from p-cresol, required a reaction temperature of 150 °C for 21 h and resulted in a significant decrease in reactivity for displacement of the second fluoride atom, which required 185 °C for displacement. Confirmation that the displacement reaction of both fluorides occurred via an SNAr mechanism was provided by 1H and 13C NMR data on the model compounds. High molecular weight, amorphous poly(arylene ether)s, bearing a pendant benzoyl group, were prepared via the reaction of 5 with a variety of bis-phenols under typical NAS conditions. The glass transition temperatures (Tg) ranged from 111 to 133 °C while the 5% weight loss temperatures ranged from 488 to 494 °C under nitrogen and from 438 to 482 °C in air.