Linear poly(aryl ether)s are generally prepared from equal mole of bisphenols and aromatic bishalides in the presence of a base. Therefore, preparing poly(aryl ether)s with a residual phenol group in the repeating unit is a challenge. In this work, we report the synthesis of a phosphinated polyether (P1) with a phenol pendent group in the repeating unit from a one-pot reaction of a BPA-based poly(ether ether ketone), poly(oxy-1,4-phenylenecarbonyl-1,4-phenyleneoxy-1,4-phenylene-isopropylidene-1,4-phenylene (BPA-PEEK), 9,10-dihydro-oxa-10-phosphaphenanthrene-10-oxide (DOPO) and phenol in the presence of sulfuric acid. The moderate-to-high molecular weight of P1 provides phenol linkages as reacting sites for epoxy resins. Subsequently, flexible and transparent films of epoxy thermosets can be prepared from the curing of P1 with three epoxy resins. The thermoset based on P1/cresol novolac epoxy shows a high T-g value (250 degrees C), a low dielectric constant (3.08), and flame retardancy (VTM-0). The moderate-to-high molecular weight of P1 is responsible for the high-T-g and flexibility of the resulting epoxy thermosets. (C) 2013 Elsevier Ltd. All rights reserved.