A new monomer di((carboxyphenoxy) tetrakis(4-fluorophenoxy)cyclotriphosphazene 1 was synthesized in a two-step reaction sequence. The direct polycondensation of 1 and/or 4,4'-dicarboxydiphenylether with aromatic ethers was carried out in P2O5/methanesulfonic acid (Eaton's reagent) at 120 degrees C for 3 h to give two series of aromatic poly)(ether ketone)s containing cyclotriphosphazene units. The effect of the introduction of the cyclotriphosphazene group on the solubility and thermal properties of these polymers was discussed with relation to the cyclotriphosphazene contents.