Nanoscale heterogeneities in radiation-cured diacrylate networks: Weakness or asset?

The crosslinking polymerization of multifunctional monomers is known to yield brittle matrices, therefore limiting the development of this technique for the production of high performance composite materials. Among the various possible causes of the brittleness, the spontaneous formation of nanoheterogeneities during radiation-initiated polymerization is supported by atomic force microscopy imaging and by calorimetric analyses. The controlled polymerization-induced phase separation of nanosized clusters of polyethersulfone was evaluated as a means for alleviating the inherent tendency of the diacrylate materials to fragile failure. Various homogeneous formulations including the aromatic diacrylate monomers, and polyethersulfone together with a compatible reactive diluent were prepared and polymerized by electron beam irradiation. The resulting toughened materials show optimized critical stress intensity factor (KIc) over 2 MPa m0.5, whereas the KIc value is about 1 MPa m0.5 for the unmodified reference resin.