Based on the model-compound studies, the composition of polyphosphoric acid (PPA)/P2O5 mixture as an effective catalytic/dehydrative medium for the preparation of poly(ether-ketones) was optimized. Thus, with the optimal weight ratio of 4:1 (PPA:P2O5), the electrophilic substitution polycondensation of 3-phenoxybenzoic acid and related AB monomers was substantially promoted at 130 degreesC to yield the subject polymer abbreviated as mPEK and related poly(ether-ketones) with significantly higher molecular weights. In the cases where the polymerization systems were completely homogeneous, the ensuing polycondensation was rapid and yielded high molecular weight polymers (e.g. mPEK [eta] = 2.10 dl/g) at 130 degreesC within 30 min., as compared to PPMA (phosphorus pentoxide/methanesulfonic acid) method which gave only moderate molecular weight polymers, e.g. mPEK ([eta] = 0.64 dl/g). In some cases, where the monomers and PPA/P2O5 were not fully compatible, polycondensation did proceed and reasonable molecular weight range ([eta] = 0.69-0.76 dl/g) could be achieved. However, the complete incompatibility between the poly(ether-sulfone) and PPA/P2O5 medium precluded the successful polymerization of 4-phenoxybenzenesulfonic acid. Published by Elsevier Science Ltd.