NORYL (TM) SA9000 resin is a commercialized telechelic PPO oligomer with phenyl methacrylate end groups. However, neat SA9000 thermoset is brittle after thermally curing. To find a method to enhance the toughness of neat SA9000 thermoset, three model reactions are designed. The first one is the 4-dimethylaminopyridine (DMAP)-catalyzed homopolymerization of glycidyl phenyl ether. The second one is the reaction of glycidyl phenyl ether and phenyl acetate in the presence of DMAP. The third one is the reaction of glycidyl phenyl ether and phenyl methacrylate in the presence DMAP. Through H-1 NMR analysis, the product is 1,3-diphenoxy-2-acetoxypropane and 1,3-diphenoxy-2-methacryalatepropane, respectively, for model reactions 2 and 3. According to the structure of products, we identify the reaction mechanisms between the phenyl acetate and epoxy, and between the phenyl methacrylate and epoxy. Based on the knowledge, we used two commercialized epoxy resin (DGEBA and HP7200) to copolymerize with SA9000 in the presence of DMAP and tert-butyl cumyl peroxide (TBCP). The toughness of the thermosets are significantly improved, which means the brittle drawback of neat SA9000 thermoset has been solved. Homogeneous, flexible thermosetting films with high glass transition temperatures, low dielectric constants, and extremely low dissipation factors are obtained. (C) 2018 Elsevier Ltd. All rights reserved.