Synthesis of polyphenylene ether and thioether ketones

Abstract

AbstractThe known polymerization of 4,4′‐difluorobenzophenone (DFB) with the dianion of hydroquinone to poly(phenylene ether ether ketone) (PEEK) and polymerization of either DFB with the dianion of 4,4′‐dihydroxybenzophenone or self polycondensation of the anion of 4‐hydroxy‐4′‐fluoro‐benzophenone to poly(phenylene ether ketone) (PEK) were studied in N‐cyclohexyl‐2‐pyrrolidone (CHP), which is a high‐boiling aprotic polar solvent. The formation of high‐molecular weight PEEK and PEK in this solvent was very efficient. The reactivity in CHP can be ascribed to effective solvation of metal ions rendering the anion very reactive toward nucleophilic substitution. The polymerization was extended to 4,4′‐bis(4‐fluorobenzoyl)diphenyl ether and 1,4‐bis[4‐(4‐fluorobenzoyl)phenoxy]benzene to give a high molecular weight polymer with PEK and PEEK repeating units and PEEK respectively. The polymerization of DFB with purified anhydrous sodium sulfide in CHP gave rapidly a high molecular weight poly(phenylene ketone sulfide) (PKS). In contrast, diphenyl sulfone (DPS) was not very effective in obtaining such a high molecular weight PKS even with prolonged heating, which suggests the uniqueness of CHP in promoting a high degree of polymerization.