Synthesis of a novel naphthalene‐based poly(arylene ether‐ketone) by polycondensation of 1,5‐bis(4‐fluorobenzoyl)‐2,6‐dimethylnaphthalene with bisphenol a

Abstract Synthesis of 1,5‐bis(4‐fluorobenzoyl)‐2,6‐dimethylnaphthalene (1), polycondensation of 1 with Bisphenol A, and properties of the obtained polymer were studied. Friedel–Crafts acylation of 2,6‐dimethylnaphthalene with 4‐fluorobenzoyl chloride in nitrobenzene selectivity afforded 1 in 82% yield. X‐ray single crystal structural analysis of 1 confirmed that the dibenzoylation proceeded regioselectively and two methyl groups sterically inhibited the coplanarity of the two aromatic planes. The polycondensation of 1 with Bisphenol A in toluene/N‐methyl‐2‐pyrrolidone (NMP) mixed solvent in the presence of excess potassium carbonate as a condensation reagent was carried out at 180°C for 4 h to quantitatively afford the corresponding poly(arylene ether‐ketone) (PEK) 3 with high molecular weight (M̄n∼30,000) as a slightly yellow powder. As the reaction time was prolonged, both M̄n and MWD of 3 increased and the solubility of 3 in chloroform clearly decreased. By GPC‐LALLS, M̄n of 3 obtained by the polycondensation for 16 h, was 85,000. The PEK 3 with high molecular weight was produced in a quantitative yield in a variety of solvents such as sulfolane. Water formed during the polycondensation hardly affected the yield and molecular weight of 3, although a small molecular weight decrease took place. To evaluate the special effect of the methyl groups of 3, polycondensation of 2,6‐bis(4‐fluorobenzoyl)naphthalene 2 with bisphenol A was carried out for comparison and the corresponding PEK 4 was quantitatively obtained. Whereas 3 was soluble in ordinary organic solvents such as tet‐rahydrofuran (THF), chloroform, and NMP at room temperature, 4 was insoluble in most solvents except for strong acids such as conc. sulfonic acid. The polymer 3 showed high glass transition temperature (238°C) and 5% weight loss temperature (457°C). Casting of the polymer from THF solution gave a transparent, tough, flexible, and amorphous film. © 1995 John Wiley & Sons, Inc.