writer：Fenfen Wang, Zhijun Yang, Jian Li, Chi Zhang, and Pingchuan Sun*
keywords：Polyurethane, Dynamic Bonds, solid-state NMR
source：期刊
specific source：Acs Macro Letters, 2021, 10, 510-517
Issue time：2021年

Nature embraces an intriguing strategy to create high-performance biomaterials, such as spider silk which presents an unparalleled combination of stiffness, tensile strength, and
toughness via hierarchical structures. However, to fabricate synthetic polymers with such excellent properties remains a challenging task. Inspired by the integration of multiblock
backbone and densely H-bonding assemblies in spider silk as well as the delicate iron?catecholate complexes in mussel byssus, we proposed a novel molecular design with multifunctional block modules to obtain polymer materials that exhibit excellent mechanical property, self-healing ability, and reprocessability. It was achieved by introducing reversible iron?catechol (DOPA?Fe3+) cross-links and quadruple H-bonds bearing 2-ureido-4-[1H]-pyrimidinone (UPy) dimers as multifunctional blocks into a segmented polyurethane backbone with urethane blocks and semicrystalline polycaprolactone (PCL) blocks. These two types of
dynamic cross-linking knots served as the sacrificial bonds to dissipate energy efficiently under external stress burden, endowing the dual physical cross-linked networks with increased toughness and breaking elongation. Moreover, the DOPA?Fe3+ complexes could increase the crystallization of PCL, leading to remarkably enhanced Young’s modulus and tensile strength. Solid-state NMR revealed the formation of quadruple H-bonds in UPy dimers and the presence of DOPA?Fe3+ complexes, which restricted the mobility of the mobile phase and enhanced the crystallinity of the PCL domain. This work provides a feasible way to develop bioinspired materials with self-healable and reprocessable features, in addition to balanced enhancement of both stiffness and toughness.