Using the dynamic bond to access macroscopically responsive structurally dynamic polymers

Wojtecki, Rudy J.; Meador, Michael A.; Rowan, Stuart J.

doi:10.1038/nmat2891

Cited by 1,418 publications

(1,174 citation statements)

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“…1,10 Non-covalent interactions have also emerged as a useful design tool for stimuli-responsive functional polymers. 11 Notable examples include mechanochromic blends containing selfassembled excimer-forming dyes that can be dispersed upon mechanical deformation, 12 healable polymers based on supramolecular motifs, which are presumed to dissociate upon application of excessive mechanical force, 13 and the mechanochemically activated dissociation of coordination polymers, which are useful for mechanically activated catalysis. 2b,2d,3,14 Here, we demonstrate that highly dynamic metallosupramolecular polymer networks based on weakly-coordinating metal-ligand complexes can also exhibit useful mechanochemical transduction.…”

Section: Introductionmentioning

confidence: 99%

Mechanochemistry with Metallosupramolecular Polymers

et al. 2014

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ABSTRACT:The transduction of mechanical force into useful chemical reactions is an emerging design approach to impart soft materials with new functions. Here, we report that mechanochemical transductions can be achieved in metallosupramolecular polymers. We show that both reversible and irreversible reactions are possible and useful to create mechanically responsive materials that display new functions. The metallopolymer studied was a crosslinked network assembled from a europium salt and a telechelic poly(ethylene-co-butylene) with 2,6-bis(1′-methylbenzimidazolyl)pyridine (Mebip) ligands at the termini. The Eu 3+ complexes serve both as mechanically responsive binding motifs and built-in optical probes that can monitor the extent of (dis)assembly due to their characteristic photoluminescent properties. Indeed, dose-dependent and reversible metal-ligand dissociation occurs upon exposure to ultrasound in solution. The absence of ultrasound-induced dissociation of a low-molecular weight model complex and in-depth studies of temperature effects confirm that the dissociation is indeed the result of mechanical activation. The influence of the strength of the metal-ligand interactions on the mechanically induced dissociation was also explored. Metallopolymers in which the Mebip ligands were substituted with more strongly coordinating dipicolinate (dpa) ligands do not dissociate upon exposure to ultrasound. Finally we show that mechanochemical transduction in metallosupramolecular polymers is also possible in the solid state. We demonstrate mending of damaged objects through ultrasound as well as mechanochromic behavior based on metal-exchange reactions in metallopolymers imbibed with an auxiliary metal salt.

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Section: Introductionmentioning

confidence: 99%

Mechanochemistry with Metallosupramolecular Polymers

et al. 2014

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“…Because the rates of the final two steps are inversely proportional to the molecular mass, healing is generally slow and inefficient. This problem can be overcome by exploiting thermally reversible, covalent bonds 7,8 or non-covalent supramolecular motifs 5,9,10 that allow the reaction equilibrium to be temporarily shifted to lower-molecular-mass species 11 on exposure to heat. This reduces the viscosity of the material, such that defects can be mended, before the equilibrium is shifted back and the polymer is reformed.…”

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confidence: 99%

Optically healable supramolecular polymers

Burnworth

Tang

Kumpfer

et al. 2011

Nature

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Polymers with the ability to repair themselves after sustaining damage could extend the lifetimes of materials used in many applications 1 . Most approaches to healable materials require heating the damaged area [2][3][4] . Here we present metallosupramolecular polymers that can be mended through exposure to light. They consist of telechelic, rubbery, low-molecular-mass polymers with ligand end groups that are non-covalently linked through metal-ion binding. On exposure to ultraviolet light, the metal-ligand motifs are electronically excited and the absorbed energy is converted into heat. This causes temporary disengagement of the metal-ligand motifs and a concomitant reversible decrease in the polymers' molecular mass and viscosity 5 , thereby allowing quick and efficient defect healing. Light can be applied locally to a damage site, so objects can in principle be healed under load. We anticipate that this approach to healable materials, based on supramolecular polymers and a light-heat conversion step, can be applied to a wide range of supramolecular materials that use different chemistries.The healing of cracks in amorphous polymers by heating above the glass transition temperature (T g ) involves surface rearrangement and approach of polymer chains, followed by wetting, diffusion and reentanglement of the chains 6 . Because the rates of the final two steps are inversely proportional to the molecular mass, healing is generally slow and inefficient. This problem can be overcome by exploiting thermally reversible, covalent bonds 7,8 or non-covalent supramolecular motifs 5,9,10 that allow the reaction equilibrium to be temporarily shifted to lower-molecular-mass species 11 on exposure to heat. This reduces the viscosity of the material, such that defects can be mended, before the equilibrium is shifted back and the polymer is reformed. Supramolecular polymers that phase separate into physically crosslinked networks (Fig. 1a) should be especially well suited for this purpose, because such morphologies generally bestow the material with high toughness. The supramolecular motifs can disengage in the solid state on exposure to heat or a competitive binding agent 12,13 , causing disassembly into small molecules 14 and viscosity reductions. Reporting a series of supramolecular materials formed by metal-ligand interactions, we demonstrate here that this architecture is an excellent basis for elastomeric materials in which defects can be efficiently repaired. We show that the use of light 15 as a stimulus for the dissociation of supramolecular motifs has distinct advantages over thermally healable systems, including the possibility of exclusively exposing and healing the damaged region.The new polymers are based on a macromonomer comprising a rubbery, amorphous poly(ethylene-co-butylene) core with 2,6-bis(19-methylbenzimidazolyl)pyridine (Mebip) ligands at the termini (Fig. 1b, 3). This design was based on the assumption that the hydrophobic core and the polar metal-ligand motif would phase separate 16 . Metal-Mebip com...

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“…However, the captured metal ions/clusters are always tightly fastened in the pores via stable covalent interactions, and cannot handle flexible modifications. In dynamic chemistry, the term “dynamic bond” can be defined as a class of bond that can selectively undergo reversible breaking and reformation upon exposure to certain environmental factors 10. Reversible or dynamic covalent chemistry involving such “dynamic bond” has a long history in polymer science, and a wide range of stimuli‐responsive materials with many different mechanisms to “read” and respond to the input stimulus have been exploited 11.…”

Section: Introductionmentioning

confidence: 99%

A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu³⁺ Ions

Zhu

Song

et al. 2015

Advanced Science

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Stimuli‐responsive structural transformations are emerging as a scaffold to develop a charming class of smart materials. A EuL metal‐organic framework (MOF) undergoes a reversible temperature‐stimulated single‐crystal to single‐crystal transformation, showing a specific behavior of fast capture/release of free Eu3+ in the channels at low and room temperatures. At room temperature, compound 1a is obtained with one free carboxylate group severing as further hook, featuring one‐dimensional square channels filled with intrinsic free europium ions. Trigged by lowering the ambient temperature, 1b is gained. In 1b, the intrinsic free europium ions can be fast captured by the carboxylate‐hooks anchored in the framework, resulting in the structural change and its channel distortion. To the best of our knowledge, this is the first report of such a rapid and reversible switch stemming from dynamic control between noncovalent and covalent Eu–ligand interactions. Utilizing EuL MOF to detect highly explosive 2,4,6‐trinitrophenol at room temperature and low temperature provides a glimpse into the potential of this material in fluorescence sensors.

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Using the dynamic bond to access macroscopically responsive structurally dynamic polymers

Cited by 1,418 publications

References 108 publications

Mechanochemistry with Metallosupramolecular Polymers

Mechanochemistry with Metallosupramolecular Polymers

Optically healable supramolecular polymers

A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu³⁺ Ions

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Using the dynamic bond to access macroscopically responsive structurally dynamic polymers

Cited by 1,418 publications

References 108 publications

Mechanochemistry with Metallosupramolecular Polymers

Mechanochemistry with Metallosupramolecular Polymers

Optically healable supramolecular polymers

A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu3+ Ions

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Product

Resources

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A Temperature‐Responsive Smart Europium Metal‐Organic Framework Switch for Reversible Capture and Release of Intrinsic Eu³⁺ Ions