Poly(Aryl ether-phenylquinoxalines)

A general method for the preparation of poly(aryl ether-phenylquinoxalines) has been developed in which the generation of the aryl ether linkage is the polymer-forming reaction. We found that the electron-deficient pyrazine component of the quinoxaline ring system activated the 6- or 7-fluoro substituent toward nucleophilic aromatic substitution. Facile displacement occurred at these positions since the pyrazine ring canstabilize the negative charge developed in the transition state through a Meisenheimer-like complex, analogous to conventional activating groups (e.g. sulfone, carbonyl).Fluoro-substituted bis-quinoxalines, 1,4- and l,3-bis(6-fluoro-3-phenyl-2-quinoxalinyl)benzene, were prepared and subjected to fluoro displacement with various bisphenoxides in N-methyl-2-pyrrolidone (NMP). High molecular weight polymers were obtained,with Tg's ranging from 230 to 315 °C. The thermal stability for the resulting materials was comparable to other poly(phenylquinoxalines) with polymer decomposition temperatures in the 480-500 °C range. This synthetic route affords the poly(phenylquinoxaline) analogue of poly(ether-imide) and the polymers show many of the same desirable characteristics (e.g. processing and ductile mechanical properties). © 1990, American Chemical Society. All rights reserved.