This study reports a method to prepare fully aromatic poly(ether ketone) thermosets. The cyclization of 2',5'-dimethoxy[1,1'-biphenyl]-2,5-diol and a difluoro monomer was carried out under pseudo high dilution condition. Two types of fully aromatic poly(ether ketone)s with macrocycle were successfully prepared by copolymerization of macrocycle of aryl ether ketone containing hydroxyphenyl groups, 4,4'-(hexafluoroisopropylidene)diphenol (HFBPA), and 4,4-difluorobenzophenone. The obtained copolymers have high molecular mass, good solubility, and high glass transition temperatures in the presence of CsF, the crosslinking reaction of copolymers occurred and afforded fully aromatic thermoset poly(aryl ether ketone)s by ring-opening reaction driven by entropy. After crosslinking, these copolymers show much higher glass transition temperatures, excellent thermal stability, and better mechanical strength. (C) 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7002-7010, 2008