Self-healing materials: a review

Wool, Richard P.

doi:10.1039/b711716g

Cited by 881 publications

(619 citation statements)

References 121 publications

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“…We synthesized macromonomer 3 (number-average molecular mass, M n 5 4,800 g mol 21 ) via a Mitsunobu reaction of 1 and hydroxyl-terminated poly (ethylene-co-butylene) (2, M n 5 4,000 g mol 21 3 Cl/CH 3 CN mixture. Films 350-400 mm thick were produced by casting and drying these solutions and compression moulding the resulting solids at 120 uC.…”

Section: Methods Summarymentioning

confidence: 99%

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Optically healable supramolecular polymers

Burnworth

Tang

Kumpfer

et al. 2011

Nature

1,621

1,327

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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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Section: Methods Summarymentioning

confidence: 99%

“…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.…”

mentioning

confidence: 99%

Optically healable supramolecular polymers

Burnworth

Tang

Kumpfer

et al. 2011

Nature

1,621

1,327

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“…Surfaces that switch between superhydrophobicity and hydrophilicity have been developed using, for example, photoresponsive surfaces with inorganic oxides and photoreactive organic molecules (Wang et al 2007), copolymer films sensitive to pH (Xia et al 2006) or electric field (electrowetting; Bhushan & Ling 2008). These surfaces can be used, for example, to control fluid flow in micro/ nanochannel networks in micro/nanofluidic chips.…”

Section: Superhydrophobicity Self-cleaning and Low Adhesionmentioning

confidence: 99%

“…Various self-healing artificial materials are being developed (Wool 2008;van der Zwaag et al in press). In polymers and polymer composites, based on Youngblood & Sottos (2008), two approaches are being pursued.…”

Section: (I ) Spiderwebmentioning

confidence: 99%

Biomimetics: lessons from nature–an overview

Bhushan

2009

Phil. Trans. R. Soc. A.

1,109

733

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Nature has developed materials, objects and processes that function from the macroscale to the nanoscale. These have gone through evolution over 3.8 Gyr. The emerging field of biomimetics allows one to mimic biology or nature to develop nanomaterials, nanodevices and processes. Properties of biological materials and surfaces result from a complex interplay between surface morphology and physical and chemical properties. Hierarchical structures with dimensions of features ranging from the macroscale to the nanoscale are extremely common in nature to provide properties of interest. Molecularscale devices, superhydrophobicity, self-cleaning, drag reduction in fluid flow, energy conversion and conservation, high adhesion, reversible adhesion, aerodynamic lift, materials and fibres with high mechanical strength, biological self-assembly, antireflection, structural coloration, thermal insulation, self-healing and sensory-aid mechanisms are some of the examples found in nature that are of commercial interest. This paper provides a broad overview of the various objects and processes of interest found in nature and applications under development or available in the marketplace.

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“…[1] Self-repairing materials, in particular, have attracted widespread interest. [2][3][4] These materials autonomously repair themselves after incurring damage, such as microcracks or even full fractures, thus prolonging the life of the material and reducing the risk of catastrophic material failure under load.…”

Section: Introductionmentioning

confidence: 99%

Self-Reporting Materials: Protein- Mediated Visual Indication of Damage in a Bulk Polymer

Bruns

Clark

2011

Chimia

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Damage self-reporting materials are able to indicate the presence of microscopic damaged regions by easy to detect signals, such as fluorescence. Therefore, these smart materials can reduce the risk of catastrophic failure of load-bearing components, e.g. in aerospace and construction applications. We highlight here our proof-of-concept paper and we present some additional data, which shows that proteins can be used as mechanophores in solid polymeric materials. Macroscopic mechanical forces were transferred from the polymer to the embedded proteins. The biomolecules act as molecular strain sensor, giving the material the desired selfreporting property. Poly(ethylene glycol) and poly(acrylamide) (PAAm) networks were doped with small amounts of thermsosome (THS), a protein cage from the family of chaperonins, that encapsulated a pair of fluorescent proteins. THS acts as a scaffold which brings the two fluorescent proteins into distance suitable for fluorescence resonance energy transfer (FRET). Moreover, THS can be distorted by mechanic forces so that the distance between the fluorescent proteins changes, leading to a change in FRET efficiency. Using the brittle PAAm as a model system, we were able to visualize microcracks in the polymers by FRET microscopy and by fluorescence lifetime imaging. THS also stabilizes the encapsulated guest proteins against thermal denaturation, increasing their half-live at 70°C by a factor of 2.3.

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Self-healing materials: a review

Cited by 881 publications

References 121 publications

Optically healable supramolecular polymers

Optically healable supramolecular polymers

Biomimetics: lessons from nature–an overview

Self-Reporting Materials: Protein- Mediated Visual Indication of Damage in a Bulk Polymer

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