Network Reorganization of Dynamic Covalent Polymer Gels with Exchangeable Diarylbibenzofuranone at Ambient Temperature

Imato, Keiichi; Ohishi, Tomoyuki; Nishihara, Masamichi; Takahara, Atsushi; Otsuka, Hideyuki

doi:10.1021/ja5065075

Cited by 98 publications

(78 citation statements)

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“…[28] AFM observations of single-chain polystyrene particles revealed that the morphology changed to as maller coil size when the polymer solution was frozen, but recovered to that observed before freezing by heating to 100 8 8C. [33][34][35][36] Theradicals are blue-colored and show greatly reduced reactivity toward oxygen. [29,30] Somer eports have also indicated that freezing ap oly(ethylene oxide) solution induces au nique polymer chain conformation, which is only found under elongation force field.…”

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confidence: 80%

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Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

et al. 2015

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Visualization and quantitative evaluation of covalent bond scission in polymeric materials are highly important for understanding failure, fatigue, and deterioration mechanisms and improving the lifetime, durability, toughness, and reliability of the materials. The diarylbibenzofuranone-based mechanophore radical system enabled, through electron paramagnetic resonance spectroscopy, in situ quantitative evaluation of scission of the mechanophores and estimation of mechanical energy induced along polymer chains by external forces. The coagulation of polymer solutions by freezing probably generated force but did not cleave the mechanophores. On the other hand, cross-linking led to efficient propagation of the force of more than 80 kJ mol(-1) to some mechanophores, resulting their cleavage and generation of colored stable radicals. This mechanoprobe concept has the potential to elucidate other debated issues in the polymer field as well.

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confidence: 80%

“…[33][34][35][36] Theradicals are blue-colored and show greatly reduced reactivity toward oxygen. DABBF and its corresponding radicals are in equilibrium at room temperature without the formation of by-products (reversible), though the amount of radicals formed is quite small.…”

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Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

et al. 2015

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“…This may be due to network expansion and elution of cyclic oligomers formed through bond exchange between the DABBF linkages. 69 We utilized this property to investigate the polymer structure via 1 H NMR in CDCl 3 solution ( Figure S3). The composition ratio was determined to be TEA/DABBF/HDI/ PPG = 1/1.40/5.20/2.30, which was largely similar to that of the reaction mixture (1/1.5/6/3).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Self-Healing of a Cross-Linked Polymer with Dynamic Covalent Linkages at Mild Temperature and Evaluation at Macroscopic and Molecular Levels

Takahara²,

2015

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A lot of self-healing materials using dynamic bonding systems have been reported, while the focus is mainly on the macroscopic self-healing behavior such as visually recognizable healing. Because the healing originates from microscopic chemical reactions of the dynamic bonds, evaluation of the reactions in the materials is necessary for elucidation of the healing mechanisms and development of the healing ability. Herein, we demonstrated self-healing of a cross-linked polymer with diarylbibenzofuranone (DABBF)-based dynamic covalent linkages at mild temperature and investigated the healing behavior from both macroscopic and microscopic viewpoints. The macroscopic behavior was inspected by mechanical tests, and the linkage reaction (equilibrium) was evaluated by electron paramagnetic resonance measurements. These assessments revealed that the healing is strongly dependent on temperature, which is attributable to synergism between changes in the chain mobility and in the equilibrium of the incorporated linkages. These findings would be applicable to other dynamic bonding systems. ■ INTRODUCTIONMaterials with self-healing ability are particularly attractive in the field of materials science because these materials have the intrinsic capacity to repair damage done to them without intervention. Although small external and internal damages in materials generally result in irreparable damage, self-healing can obviate such risks and thereby lead to reduced waste and improved lifetime, durability, and reliability of materials. In addition, the application of self-healing materials to artificial organ and space development purposes, where there is little scope for intervention and assisted repair, is anticipated. Selfhealing of polymeric materials has been achieved by various approaches such as monomer release and subsequent polymerization, 1−3 unique entropic elasticity of slide-ring networks, 4 topological interaction of dangling chains in polymer networks, 5,6 and irreversible chemical reactions (re-cross-linking). 7−10 Similarly, reversible dynamic bonds (or interactions) have been utilized for polymer self-healing with the advantage of an unlimited number of healing times. 11 Dynamic bonding systems can be categorized into two classes: healing in the gel state with solvent and in the bulk state without solvent. Although the polymer chains in gels have higher mobility than in the bulk state and are therefore expected to exhibit better healing ability, gels generally suffer from volatilization of solvents and show lower mechanical properties, with some exceptions. 12−16 Therefore, self-healing in the bulk state is more desirable, except in cases where these materials are intended for biomaterials application. 17 Various dynamic bonds and reactions are prospectively exploitable for healing bulk polymers, including hydrogen bonding, 18,19 coordination bonds, 20 π−π stacking interactions, 21,22 Diels−Alder reactions, 23−26 disulfide bonds, 27−31 trithiocarbonate linkages, 32 alkoxyamine linkages, 33−39 siloxane chemistry, 4...

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“…The dynamic nature of the polymer also allowed introduction of a chain transfer agent to control polymerization or end group functionalization. Imato et al demonstrated that the reversible dissociation of a diarylbibenzo‐furanone into two carbon‐centered radicals can be used to create polyurethane networks that can undergo exchange at ambient temperature . The self‐healing behavior was evaluated on the macroscopic level by mechanical testing (Fig.…”

Section: Othersmentioning

confidence: 99%

Dynamic covalent polymers

García

Smulders²

2016

J. Polym. Sci. Part A: Polym. Chem.

174

159

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This Highlight presents an overview of the rapidly growing field of dynamic covalent polymers. This class of polymers combines intrinsic reversibility with the robustness of covalent bonds, thus enabling formation of mechanically stable, polymer‐based materials that are responsive to external stimuli. It will be discussed how the inherent dynamic nature of the dynamic covalent bonds on the molecular level can be translated to the macroscopic level of the polymer, giving access to a range of applications, such as stimuli‐responsive or self‐healing materials. A primary distinction will be made based on the type of dynamic covalent bond employed, while a secondary distinction will be based on the consideration whether the dynamic covalent bond is used in the main chain of the polymer or whether it is used to allow side chain modification of the polymer. Emphasis will be on the chemistry of the dynamic covalent bonds present in the polymer, in particular in relation to how the specific (dynamic) features of the bond impart functionality to the polymer material, and to the conditions under which this dynamic behavior is manifested. © 2016 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2016, 54, 3551–3577.

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Network Reorganization of Dynamic Covalent Polymer Gels with Exchangeable Diarylbibenzofuranone at Ambient Temperature

Cited by 98 publications

References 36 publications

Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

Mechanophores with a Reversible Radical System and Freezing‐Induced Mechanochemistry in Polymer Solutions and Gels

Self-Healing of a Cross-Linked Polymer with Dynamic Covalent Linkages at Mild Temperature and Evaluation at Macroscopic and Molecular Levels

Dynamic covalent polymers

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