Synthesis and properties of poly(aryl ether ketone) copolymers containing 1,5-naphthalene moieties

Poly(aryl ether ketone) copolymers possessing various compositions of 1,5-naphthalene and 1,4-phenylene moieties were prepared by the reaction of 4,4'-difluorobenzophenone with hydroquinone (HQ) and 1,5-dihydroxynaphthalene (DHN) in the presence of sodium carbonate and potassium carbonate in diphenyl sulfone. The synthesized copolymers were characterized by FT-IR spectra, differential scanning calorimetry, and thermogravimetric analysis. Thermal analyses of the copolymers showed that the glass transition temperature increased, while the melting temperature and 2.5% weight loss temperature decreased with increasing content of 1,5-naphthalene moieties. For the copolymers synthesized with the molar fraction of DHN in the dihydroxy monomers (DHN, HQ) being over 0.4, no cold crystallization temperature and melting temperature were detected, indicating that these copolymers are almost amorphous. The crystal structure of the copolymers with the molar fraction of DHN being not higher than 0.2 is rhombic, equal to poly(ether ether ketone).