Abstract
A method for the preparation of poly(aryl ether benzimidazoles) has been developed where the generation of an ether linkage is the polymer-forming reaction. We found that 2-(4-fluorophenyl)-benzimidazoles were activated toward nucleophilic aromatic substitution with phenoxides. Facile displacement occurred at this position since the benzimidazoles ring can stabilize the negative charge developed in the transition state through a Meisenheimer complex, analogous to conventional activating groups (e.g., sulfone or carbonyl). An appropriately substituted dihalo bibenzimidazole, 2,2′-bis(4-fluorophenyl)-6,6′-bibenzimidazole, was prepared and polymerized with bisphenols in aprotic dipolar solvents in the presence of K2CO3. High molecular weight polymers were obtained with glass transition temperatures ranging from 220 to 250°C. The resulting polymers were processable from solution and showed good thermal stability. This general synthetic route was also applied to AB monomers which, once polymerized, produced high polymer. This synthetic route affords the poly(benzimidazole) analogue of poly(ether imide) and shows many of the same desirable characteristics.