Epoxy resins toughened with in situ azide–alkyne polymerized polysulfones

To simultaneously improve the fracture toughness and heat resistance of a cured toughened epoxy resin along with a reduction in its viscosity during the mixing process, two novel polysulfone-type polymers are synthesized via azide–alkyne polymerization for use as toughening agents. The epoxy resin toughened with these polymers by in situ azide–alkyne polymerization during the cure process, which shows excellent processibility and based on the significantly lower viscosity (61 and 62 cP) during epoxy mixing process than that of commonly commercial polyethersulfone (PES, 127,612 cP). The novel polysulfone-type polymer toughened epoxy resin showed the advantage in excellent fracture toughness than the PES toughened epoxy. In addition, the glass transition temperature of the novel polysulfone-type polymer toughened epoxy resin is similar to that of the neat one (∼230 °C) and does not decrease, which implies excellent heat resistance of the toughened epoxy. These phenomena can be attributed to the formation of semi-interpenetrating polymer networks comprising the epoxy network and the linear polysulfone-type polymers. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45790.