A high-performance matrix is the key base for the fabrication of high-frequency copper-clad laminates. A high-performance resin system based on commercial poly(phenylene oxide) (PPO) and 2,2'-bis(4-cyanatophenyl) isopropylidene (BADCy), coded as PPO-n/BADCy (where n is the weight parts of PPO per 100 weight parts of BADCy), was developed. The effect of PPO on the key properties, including the dielectric and thermal properties, water resistance, and toughness, of the cured resins was investigated extensively. The results show that PPO not only catalyzed the curing reaction of BADCy but also reacted with BADCy to form a single-phase structure. Furthermore, compared with the cured BADCy resin with 1 phr epoxy resin as a catalyst, the cured PPO-n/BADCy resins had significantly increased impact strengths and decreased dielectric constants, loss, and water resistance. The reasons behind these desirable improvements are discussed from the view of structure-property relationships. These results suggest that the PPO-n/BADCy system has great potential to be used as a matrix for high-frequency copper-clad laminates or other advanced composites. (c) 2011 Wiley Periodicals, Inc. J Appl Polym Sci 121: 1675-1684, 2011