A new monomer containing naphthalene, namely 4,4 '-di(1-naphthoxy)benzophenone (DNOBN), was prepared by the condensation reaction of 4,4 '-difluorobenzophenone with 1-naphthol in the presence of base in N-methylpyrrolidone (NMP). Novel poly(aryl ether ketone)s containing both 2,6-naphthylene and 1,4-naphthylene units were synthesized by the electrophilic Friedel-Crafts acylation polycondensation of terephthaloyl chloride with a mixture of 2,6-bis(4-phenoxybenzoyl)naphthalene (BPOBN) and DNOBN, over a wide range of BPOBN/DNOBN molar ratios, in the presence of anhydrous AlCl3 and NMP in 1,2-dichloroethane (DCE). The copolymers obtained were characterized by different physicochemical techniques. The copolymers with 10-20 mol% DNOBN are semicrystalline and had remarkably increased T(g)s over commercially available poly(ether ether ketone) and poly(ether ketone ketone) due to the incorporation of 2,6-naphthylene and 1,4-naphthylene moieties in the main chains. The copolymer IV with 20 mol% DNOBN had not only high T-g of 189 degrees C, but also moderate T-m of 338 degrees C, having good potential for melt processing. The copolymer IV had tensile strength of 102.2 MPa, Young's modulus of 3.25 GPa, and elongation at break of 18.5% and exhibited high thermal stability and excellent resistance to organic solvents.