Synthesis and properties of novel copolymers of poly(ether ketone ketone) and poly(ether ether ketone ketone) containing amide and sulfone linkages

Abstract

N, N′-Bis(4-phenoxybenzoyl)-4,4′-diaminodiphenyl sulfone (BPBDAS) was prepared by the condensation of 4,4′-diaminodiphenyl sulfone with 4-phenoxybenzoyl chloride in N, N-dimethylacetamide. Novel copolymers of poly(ether ketone ketone) (PEKK) and poly(ether ether ketone ketone) containing amide and sulfone linkages (PEASAEKK) were synthesized by electrophilic Friedel–Crafts copolycondensation of terephthaloyl chloride with a mixture of diphenyl ether (DPE) and BPBDAS over a wide range of DPE/BPBDAS molar ratios, in the presence of anhydrous AlCl₃ and N-methylpyrrolidone in 1,2-dichloroethane. The influences of the reaction conditions on the preparation of copolymers were examined. The copolymers obtained were characterized by different physicochemical techniques. The copolymers containing 10–25 mol% BPBDAS are semicrystalline and had remarkably increased T _gs compared to the commercially available poly(ether ether ketone) and PEKK due to the incorporation of amide and sulfone linkages in the main chains. The copolymer V with 25 mol% BPBDAS had not only high T _g of 187°C but also moderate T _m of 343°C, with good potential for melt processing. The copolymer V had a tensile strength of 102.7 MPa, Young’s modulus of 2.19 GPa, and elongation at break of 14.1%, and it also exhibited high thermal stability and good resistance to organic solvents.