Supramolecularly toughened and elastic epoxy resins by grafting 2-ureido-4[1H]-pyrimidone moieties on the side chain

Multiple hydrogen bonds have been widely used to form a supramolecular network and endow materials with enhanced mechanical strength, good elasticity, and/or self-healing properties. In this study, 2-ureido-4[1H]-pyrimidone (UPy) compounds were synthesized and chemically grafted onto the side chain of epoxy resins. The UPy-modified epoxy resin demonstrated substantial improvements in toughness and elasticity compared with unmodified epoxy resin as proven by a tensile test and distortion test. The breaking elongation of the UPy-modified epoxy resin was 5 times higher than that of unmodified epoxy resin under a tensile test. In addition, the fracture mechanism of the modified epoxy resin matched with the ductile fracture rather than the brittle fracture of unmodified epoxy resins. The introduction of quadruple hydrogen bonds by chemical modification may provide a simple and effective way to design and prepare highly flexible thermosetting resin materials.