High-Performance Polymeric Materials through Hydrogen-Bond Cross-Linking

It has always been critical to develop high-performance polymeric materials with exceptional mechanical strength and toughness, thermal stability, and even healable properties for meeting performance requirements in industry. Conventional chemical cross-linking leads to enhanced mechanical strength and thermostability at the expense of extensibility due to mutually exclusive mechanisms. Such major challenges have recently been addressed by using noncovalent cross-linking of reversible multiple hydrogen-bonds (H-bonds) that widely exist in biological materials, such as silk and muscle. Recent decades have witnessed the development of many tailor-made high-performance H-bond cross-linked polymeric materials. Here, recent advances in H-bond cross-linking strategies are reviewed for creating high-performance polymeric materials. H-bond cross-linking of polymers can be realized via i) self-association of interchain multiple H-bonding interactions or specific H-bond cross-linking motifs, such as 2-ureido-4-pyrimidone units with self-complementary quadruple H-bonds and ii) addition of external cross-linkers, including small molecules, nanoparticles, and polymer aggregates. The resultant cross-linked polymers normally exhibit tunable high strength, large extensibility, improved thermostability, and healable capability. Such performance portfolios enable these advanced polymers to find many significant cutting-edge applications. Major challenges facing existing H-bond cross-linking strategies are discussed, and some promising approaches for designing H-bond cross-linked polymeric materials in the future are also proposed.