Synthesis and properties of novel poly(aryl ether ketone)s containing both 2,6-naphthylene and 1,4-naphthylene units

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 _gs 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°C, but also moderate T _m of 338°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.