Self-healing and thermoreversible rubber from supramolecular assembly
TL;DR: The design and synthesis of molecules that associate together to form both chains and cross-links via hydrogen bonds and the system shows recoverable extensibility up to several hundred per cent and little creep under load are designed and synthesized.
Abstract: Rubbers exhibit enormous extensibility up to several hundred per cent, compared with a few per cent for ordinary solids, and have the ability to recover their original shape and dimensions on release of stress. Rubber elasticity is a property of macromolecules that are either covalently cross-linked or connected in a network by physical associations such as small glassy or crystalline domains, ionic aggregates or multiple hydrogen bonds. Covalent cross-links or strong physical associations prevent flow and creep. Here we design and synthesize molecules that associate together to form both chains and cross-links via hydrogen bonds. The system shows recoverable extensibility up to several hundred per cent and little creep under load. In striking contrast to conventional cross-linked or thermoreversible rubbers made of macromolecules, these systems, when broken or cut, can be simply repaired by bringing together fractured surfaces to self-heal at room temperature. Repaired samples recuperate their enormous extensibility. The process of breaking and healing can be repeated many times. These materials can be easily processed, re-used and recycled. Their unique self-repairing properties, the simplicity of their synthesis, their availability from renewable resources and the low cost of raw ingredients (fatty acids and urea) bode well for future applications.
Citations
More filters
TL;DR: The specific features of supramolecular polymers that can lead to applications in a variety of fields are reviewed, including: materials—in which processability and self-healing properties are of interest; biomedicine— in which the concerns are dynamic functionality and biodegradability; and hierarchical assembly and electronic systems—with an interest in unidirectionality of charge flow.
Abstract: Supramolecular polymers can be random and entangled coils with the mechanical properties of plastics and elastomers, but with great capacity for processability, recycling, and self-healing due to their reversible monomer-to-polymer transitions. At the other extreme, supramolecular polymers can be formed by self-assembly among designed subunits to yield shape-persistent and highly ordered filaments. The use of strong and directional interactions among molecular subunits can achieve not only rich dynamic behavior but also high degrees of internal order that are not known in ordinary polymers. They can resemble, for example, the ordered and dynamic one-dimensional supramolecular assemblies of the cell cytoskeleton and possess useful biological and electronic functions.
2,777 citations
TL;DR: Electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin akin to human skin.
Abstract: Human skin is a remarkable organ. It consists of an integrated, stretchable network of sensors that relay information about tactile and thermal stimuli to the brain, allowing us to maneuver within our environment safely and effectively. Interest in large-area networks of electronic devices inspired by human skin is motivated by the promise of creating autonomous intelligent robots and biomimetic prosthetics, among other applications. The development of electronic networks comprised of flexible, stretchable, and robust devices that are compatible with large-area implementation and integrated with multiple functionalities is a testament to the progress in developing an electronic skin (e-skin) akin to human skin. E-skins are already capable of providing augmented performance over their organic counterpart, both in superior spatial resolution and thermal sensitivity. They could be further improved through the incorporation of additional functionalities (e.g., chemical and biological sensing) and desired properties (e.g., biodegradability and self-powering). Continued rapid progress in this area is promising for the development of a fully integrated e-skin in the near future.
1,950 citations
TL;DR: There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging.
Abstract: Renewable resources are used increasingly in the production of polymers. In particular, monomers such as carbon dioxide, terpenes, vegetable oils and carbohydrates can be used as feedstocks for the manufacture of a variety of sustainable materials and products, including elastomers, plastics, hydrogels, flexible electronics, resins, engineering polymers and composites. Efficient catalysis is required to produce monomers, to facilitate selective polymerizations and to enable recycling or upcycling of waste materials. There are opportunities to use such sustainable polymers in both high-value areas and in basic applications such as packaging. Life-cycle assessment can be used to quantify the environmental benefits of sustainable polymers.
1,651 citations
TL;DR: It is reported that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties.
Abstract: Hydrogels attract great attention as biomaterials as a result of their soft and wet nature, similar to that of biological tissues. Recent inventions of several tough hydrogels show their potential as structural biomaterials, such as cartilage. Any given application, however, requires a combination of mechanical properties including stiffness, strength, toughness, damping, fatigue resistance and self-healing, along with biocompatibility. This combination is rarely realized. Here, we report that polyampholytes, polymers bearing randomly dispersed cationic and anionic repeat groups, form tough and viscoelastic hydrogels with multiple mechanical properties. The randomness makes ionic bonds of a wide distribution of strength. The strong bonds serve as permanent crosslinks, imparting elasticity, whereas the weak bonds reversibly break and re-form, dissipating energy. These physical hydrogels of supramolecular structure can be tuned to change multiple mechanical properties over wide ranges by using diverse ionic combinations. This polyampholyte approach is synthetically simple and dramatically increases the choice of tough hydrogels for applications.
1,496 citations
TL;DR: This work presents metallosupramolecular polymers that can be mended through exposure to light, which consist of telechelic, rubbery, low-molecular-mass polymers with ligand end groups that are non-covalently linked through metal-ion binding.
Abstract: Smart materials with an in-built ability to repair damage caused by normal wear and tear could prove useful in a wide range of applications. Most healable polymer-based materials so far developed require heating of the damaged area. But Burnworth et al. have now produced materials — in the form of polymer strands linked through metal complexes — that can be mended through exposure to light. The metal complexes in these materials can absorb ultraviolet light that is then converted into heat, which temporarily unlinks the polymer strands for quick and efficient defect healing. In principle, healing can take place in situ and while under load. Polymers with the ability to repair themselves after sustaining damage could extend the lifetimes of materials used in many applications1. Most approaches to healable materials require heating the damaged area2,3,4. 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 viscosity5, 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.
1,476 citations
References
More filters
26 May 1995
TL;DR: From molecular to supramolescular chemistry: concepts and language of supramolecular chemistry, molecular recognition, information, complementarity molecular receptors - design principles and more.
Abstract: Part 1 From molecular to supramolecular chemistry: concepts and language of supramolecular chemistry. Part 2 Molecular recognition: recognition, information, complementarity molecular receptors - design principles spherical recognition - cryptates of metal cations tetrahedral recognition by macrotricyclic cryptands recognition of ammonium ions and related substrates binding and recognition of neutral moelcules. Part 3 Anion co-ordination chemistry and the recognition of anionic substrates. Part 4 Coreceptor molecules and multiple recognition: dinuclear and polynuclear metal ion cryptates linear recognition of molecular length by ditopic coreceptors heterotopic coreceptors - cyclophane receptors, amphiphilic receptors, large molecular cage multiple recognition in metalloreceptors supramolecular dynamics. Part 5 Supramolecular reactivity and catalysis: catalysis by reactive macrocyclic cation receptor molecules catalysis by reactive anion receptor molecules catalysis with cyclophane type receptors supramolecular metallo-catalysis cocatalysis - catalysis of synthetic reactions biomolecular and abiotic catalysis. Part 6 Transport processes and carrier design: carrier-mediated transport cation-transport processes - cation carriers anion transport processes - anion carriers coupled transport processes electron-coupled transpoort in a redox gradient proton-coupled transport in a pH gradient light-coupled transport processes transfer via transmembrane channels. Part 7 From supermolecules to polymolecular assemblies: heterogeneous molecular recognition - supramolecular solid materials from endoreceptors to exoreceptors - molecular recognition at surfaces molecular and supramolecular morphogenesis supramolecular heterogeneous catalysis. Part 8 Molecular and supramolecular devices: molecular recognition, information and signals - semiochemistry supramolecular photochemistry - molecular and supramolecular photonic devices light conversion and energy transfer devices photosensitive molecular receptors photoinduced electron transfer in photoactive devices photoinduced reactions in supramolecular species non-linear optical properties of supramolecular species supramolecular effects in photochemical hole burning molecular and supramolecular electronic devices supramolecular electrochemistry electron conducting devices - molecular wires polarized molecular wires - rectifying devices modified and switchable molecular wires molecular magnetic devices molecular and supramolecular ionic devices tubular mesophases. (Part contents).
8,168 citations
TL;DR: 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems.
Abstract: Units of 2-ureido-4-pyrimidone that dimerize strongly in a self-complementary array of four cooperative hydrogen bonds were used as the associating end group in reversible self-assembling polymer systems. The unidirectional design of the binding sites prevents uncontrolled multidirectional association or gelation. Linear polymers and reversible networks were formed from monomers with two and three binding sites, respectively. The thermal and environmental control over lifetime and bond strength makes many properties, such as viscosity, chain length, and composition, tunable in a way not accessible to traditional polymers. Hence, polymer networks with thermodynamically controlled architectures can be formed, for use in, for example, coatings and hot melts, where a reversible, strongly temperature-dependent rheology is highly advantageous.
2,011 citations
TL;DR: Etude theorique de la dynamique de the relaxation de contrainte dans un systeme dense de polymeres vivants as mentioned in this paper, e.g.
Abstract: Etude theorique de la dynamique de la relaxation de contrainte dans un systeme dense de polymeres vivants
884 citations
TL;DR: In this article, the authors developed a theory of "sticky reptation" to model the dynamics of entangled solutions of associating polymers with many stickers per chain, which predicts a very strong concentration dependence of viscosity in good agr...
Abstract: The process of making and breaking reversible bonds between associating groups (stickers) controls the dynamics of associating polymers. We develop a theory of “sticky reptation” to model the dynamics of entangled solutions of associating polymers with many stickers per chain. At a high degree of association, there are very few unassociated stickers. It is therefore very difficult for a sticker to find a new partner to associate with after breaking the bond with an old one. Typically a sticker returns to its old partner following an unsuccessful search for a new one, prolonging the effective lifetime of reversible bonds. In the sticky reptation model, the search for a new partner is restricted to a part of the tube confining the entangled chain. Another important effect is the increase of the fraction of the interchain associations at the expense of the intrachain ones with increasing polymer concentration. The sticky reptation model predicts a very strong concentration dependence of viscosity in good agr...
440 citations