Synthesis and properties of novel random copolymers of poly(ether ketone ether ketone ketone)–poly(ether ketone imide)

Bis[4-(p-phenoxybenzoyl)-1,2-benzenedioyl]-N,N,N',N'-4,4'-diaminodiphenyl ether (BPBDADPE) was prepared by the Friedel-Crafts acylation reaction of diphenyl ether (DPE) with bis(4-chloroformyl-1,2-benzenedioyl)-N,N,N',N'-4,4'-diaminodiphenyl ether (BCBDADPE). Novel random copolymers of poly(ether ketone ether ketone ketone)(PEKEKK)–poly(ether ketone imide)(PEKI) were synthesized by the modified electrophilic Friedel-Crafts copolycondensation of terephthaloyl chloride (TPC) with a mixture of 4,4'-diphenoxybenzophenone (DPOBPN) and BPBDADPE, over a wide range of DPOBPN/BPBDADPE molar ratios, in the presence of anhydrous aluminum chloride and N-methylpyrrolidone (NMP) in 1,2-dichloroethane (DCE). The random copolymers with 10–40 mol% BPBDADPE are semicrystalline and had much higher Tgs than those of the conventional PEEK and PEKK due to the incorporation of imide linkages in the main chains. The copolymers IV and V with 30–40 mol% BPBDADPE had not only high Tgs of 185–188 °C, but also moderate Tms of 338–340 °C, having good potential for melt processing. The copolymers IV and V had tensile strengths of 102.1–105.3 MPa, Young’s moduli of 2.22–2.43 GPa, and elongations at break of 14.1–15.9 % and exhibited high thermal stability and good resistance to organic solvents.