Evading the strength-ductility trade-off dilemma of rigid thermosets by incorporating triple cross-links of varying strengths

Synchronously improving the mechanical strengths and ductility of rigid thermoset materials is a difficult and long-standing problem in polymer science. Inspired by mussel byssal threads, this study proposes a new class of rigid thermosets composed of three types of cross-links. Two of these cross-links are formed from reversible hydrogen bonds of varying strengths, and the third is constructed from covalent bonds. Synergetic interplay among the hierarchical hydrogen bonds enhances the speed and efficiency of energy dissipation of polymer networks. Consequently, the coexisting covalent cross-links and hierarchical hydrogen bonds simultaneously improve both the strength and ductility of the polymer materials, thus avoiding the strength-ductility trade-off dilemma.