Coordination Bonds and Diels–Alder Bonds Dual Crosslinked Polymer Networks of Self‐healing Polyurethane

Abstract

A dual crosslinked self‐healing polyurethane was prepared with robust mechanical properties through the dynamic reversible pyridine‐Fe3+ coordination bonds and Diels–Alder (DA) covalent bonds dual crosslinking strategy. Moreover, the mechanical properties and self‐healing ability of polyurethane can be tuned readily by different ratio of the coordination bonds and DA bonds. Under external load, the coordination bonds serve as sacrificial bonds are broken to dissipate energy, the DA bonds can keep the shape of sample. With the coordination bonds participation, the damaged samples can be healed under moderate heating treatment or with the aid of FeCl3 solution. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2019, 57, 2228–2234

Evolution of self-healing elastomers, from extrinsic to combined intrinsic mechanisms: a review

“…Other non-covalent systems were used as ionic interactions combined with DA chemistry in an acrylic copolymer. 211 In the last year, metal-ligand coordination has also been combined with different covalent systems and matrices such as ENR (with boron-based bonds 212 ), PDMS (with imine bonds 213 ), PU (with DA chemistry 214 ) and PUU (with disulfide bonds 215 ), but with very different results that limit establishing yet a clear trend for these combinations.…”

Optimizing the fracture toughness of a dual cross-linked hydrogel via molecular dynamics simulation

“…Finally, double network polymers have been prepared which also have excellent mechanical strength and self-healing properties. 19,20 To understand the inner mechanism of the high toughness, it is necessary to characterize the structure change of the physical network, the chemical network and the voids during the tensile process. However, they are difficult to be analyzed by experimental methods.…”

Thermodynamics and Stereochemistry of Diels–Alder Polymer Networks: Role of Crosslinker Flexibility and Crosslinking Density

“…Dynamic covalent polymer networks (DCPNs) are intrinsically reversible and possess the ability for covalent bond network rearrangement. − This rearrangement and reversibility enable these dynamic covalent networks to break the traditional boundary between thermoplastic and thermosetting polymers, offering new opportunities in adaptable materials. ,, In fact, recent progress in the development of dynamic networks has already lead to novel self-healing polymers, − shape-morphing materials, − and 3D-printable crosslinking networks. − Depending on the nature of the dynamic bonds, DCPNs can be categorized into associative or dissociative networks. , Associative dynamic networks undergo crosslink shuffling via catalyzed bond exchange, with the number of dynamic bonds remaining constant during network rearrangement, which, for example, occurs during reprocessing of vitrimers. , Dissociative dynamic networks, on the other hand, reversibly dissociate and reform the network to achieve rearrangement. , Among many dynamic covalent bonds, Diels–Alder (DA) reactions present one of the most important families of dissociative dynamic bonding, mainly due to their catalyst-free nature and the absence of low-molecular-weight side products. − The thermoreversible DA reaction of interest to this work involves cycloaddition between furan, a conjugated diene, and maleimide, a dienophile. The reaction exhibits high conversion rates at ambient temperature ,, and has “click” characteristics, enabling DA polymer (DAP) networks with robust mechanical properties.…”