High curing temperature is the key drawback of present heat resistant thermosetting resins. A novel epoxy-functionalized hyperbranched poly(phenylene oxide), coded as eHBPPO, was synthesized, and used to modify 2,2'-bis (4-cyanatophenyl) isopropylidene (CE). Compared with CE, CE/eHBPPO system has significantly decreased curing temperature owing to the different curing mechanism. Based on this results, cured CE/eHBPPO resins without postcuring process, and cured CE resin postcured at 230 degrees C were prepared, their dynamic mechanical and dielectric properties were systematically investigated. Results show that cured CE/eHBPPO resins not only have excellent stability in dielectric properties over a wide frequency range (1-10(9)Hz), but also show attractively lower dielectric constant and loss than CE resin. In addition, cured CE/eHBPPO resins also have high glass transition temperature and storage moduli in glassy state. These attractive integrated performance of CE/eHBPPO suggest a new method to develop high performance resins. (C) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 123: 2351-2359, 2012