Synthesis and properties of poly(arylene-ether-ketone)s containing a dimethylnaphthalene skeleton in the main chain

The synthesis of novel dihaloarenes (1,5-bis(4-halophenyl)-2,6-dimethylnaphthalenes 1), polycondensation of 1 with biphenols, and properties of the obtained polymers were described. Selectively Friedel-Crafts acylation of 2,6-dimethylnaphthalene with 4-halobenzoyl chlorides in nitrobenzene afforded 1 in high yields. X-Ray single-crystal structural analysis of 1 supported that the dibenzoylation proceeded regioselectively at the 1- and 5-positions and the two methyl groups sterically inhibited the coplanarity of the aromatic planes. The polycondensation of 1a 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 degrees C for several hours to quantitatively afford the corresponding poly(arylene-ether-ketone) (PEK) 3 with a high molecular weight (M(n) -30,000) as a slightly yellow powder. To evaluate the 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 obtained quantitatively. Whereas 3 was soluble in ordinary organic solvents such as tetrahydrofuran (THF) and chloroform at room temperature, 4 was insoluble in common solvents except for strong acids such as cone. sulfonic acid. 3 showed a high glass-transition temperature (238 degrees C) and a 5% weight loss temperature of 457 degrees C, The polycondensations of 1a with various biphenols such as dihydroxybenzophenone were carried out to examine the properties of the obtained polymers, The obtained PEKs showed high glass transition temperatures and 5% weight loss temperatures as well as good solubilities in ordinary organic solvents at room temperature. Casting of the polymers from THF solution gave transparent, tough, flexible, and amorphous films. 1,5-Bis(4-chlorobenzoyl)-2,6-dimethylnaphthalene 1b similarly underwent a polycondensation reaction with Bisphenol A to give the corresponding polymer quantitatively.