The view on macromolecules has expanded significantly since Staudinger's hypothesis 100 years ago. Currently noncovalent bonds are ranked equally important to their covalent counterparts, in ...particular in view of controlling macromolecules structure and assembly by pure force. With Staudinger's work expanded by mechanically driven bond-rupture in macromolecules, applications of mechanophores are highlighted in view of interfaces, stress-detection, vitrimers and self-healing. Selected underlying processes of mechanochemical and mechanobiological activation in macromolecules are discussed.
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•The view on macromolecules has expanded significantly since Staudinger's hypothesis 100 years ago.•Mechanically induced bond-rupture features applications in interfacial stress-detection, vitrimers and self-healing materials.•Both, mechanochemical and mechanobiological activation of bonds is important in polymer-science and cell-biology.•Dynamic properties of mechanophores in polymers triggers self-healing responses enabling a longer usage time.•Staudingers vision will enable polymers as attractive materials for another 100 years.
Self‐Healing in Supramolecular Polymers Campanella, Antonella; Döhler, Diana; Binder, Wolfgang H.
Macromolecular rapid communications.,
September 2018, Letnik:
39, Številka:
17
Journal Article
Recenzirano
Adaption and self‐healing are two major principles in material science, often coupled with the placement of supramolecular moieties within a material. Proper molecular design can enable self‐healing ...within such materials, displaying enormous potential in technology and application. Here, basic physicochemical aspects as well as new material developments in the field are described, published after a recent review in Macromolecular Rapid Communications in 2013.
What makes a supramolecular material self‐healing? This article provides insight into this complex question, discussing the dynamics of supramolecular entities within a material, together with newly reported work in the field since 2013.
Vesicles can be individually fabricated from naturally occurring lipid or synthetic block copolymer molecules via self‐assembly in aqueous solutions; the blending of both vesicle‐forming amphiphiles ...leads to the formation of hybrid membranes. Their final stabilities and lateral morphologies are strongly determined by the molar composition, size, and charge properties of the interacting components as well as by the lipid chain melting temperature. Upon merging the best properties of lipo‐ and polymersomal membranes, hybrid lipid/polymer vesicles represent a new scaffold for medical applications combining, e.g., combining the biocompatibility of liposomes with the high thermal and mechanical stability and functional variability of polymersomes within a single vesicle type. Up to now, several hybrid membrane systems and their corresponding vesicular morphologies have been studied, highlighting the attractive properties and features useful in selective delivery receptor scaffolding.
Merging the properties of lipo‐ and polymersomal membranes, hybrid lipid/polymer vesicles represent an approach towards advanced delivery and encapsulation systems, combining the biocompatibility of liposomes with the high thermal and mechanical stability and functional variability of polymersomes in a single vesicle type. Several hybrid membrane systems and their morphologies together with their phase properties are discussed, also in terms of their underlying membrane properties in view of biological applications.
“Click” chemistry represents one of the most powerful approaches for linking molecules in chemistry and materials science. Triggering this reaction by mechanical force would enable site‐ and ...stress‐specific “click” reactions—a hitherto unreported observation. We introduce the design and realization of a homogeneous Cu catalyst able to activate through mechanical force when attached to suitable polymer chains, acting as a lever to transmit the force to the central catalytic system. Activation of the subsequent copper‐catalyzed “click” reaction (CuAAC) is achieved either by ultrasonication or mechanical pressing of a polymeric material, using a fluorogenic dye to detect the activation of the catalyst. Based on an N‐heterocyclic copper(I) carbene with attached polymeric chains of different flexibility, the force is transmitted to the central catalyst, thereby activating a CuAAC in solution and in the solid state.
Feeling the pressure: A pressure‐sensitive homogeneous CuI “click” catalyst activated by mechanical force through attached polymer chains has been developed. The attached polymer chains transmit the mechanical force directly to the central catalytic Cu carbene, which in turn activates the “click” reaction, both in solution and in the solid state.
Hydrogen bonds (H-bonds) constitute highly relevant structural units of molecular self-assembly. They bridge biological and synthetic sciences, implementing dynamic properties into materials and ...molecules, not achieved via purely covalent bonds. Phase segregation on the other hand represents another important assembly principle, responsible for, e.g., cell compartimentation, membrane-formation, and microphase segregation in polymers. Yet, despite the expanding elegant synthetic strategies of supramolecular polymers, the investigation of phase behavior of macromolecules driven by H-bonding forces still remains in its infancy. Compared to phase segregation arising from covalently linked block copolymers, the generation of phase segregated nanostructures via supramolecular polymers facilitates the design of novel functional materials, such as those with stimuli-responsive, self-healing, and erasable-material properties. We here discuss the phase segregation of H-bonding polymers in both the solution and solid state, wherein the molecular recognition elements are based on multiple H-bonding moieties, such as thymine/2,6-diamino-pyridine (THY/DAP), thymine/diamino triazine (THY/DAT), and barbiturate/Hamilton wedge (Ba/HW) elements. The specific aggregation of a series of different H-bonding polymers in solution, both linear and dendritic polymers, bearing heterocomplementary H-bonding moieties are described, in particular focusing on the issue of phase segregation. The exploitation of H-bonded supramolecular dendrons with segregating polymer chains leads to the formation of three-phase segregated hierarchical micelles in solution, purely linking the components via H-bonds, in turn displaying a versatile spectrum of segregated morphologies. We also focus on segregation effects of H-bonded amorphous and crystalline polymers: thus the formation of nanostructures, such as disordered micelles and well-ordered body centered cubic (BCC) packed spheres from telechelic polymers bearing H-bonding moieties at the chain ends is observed. Finally, we discuss the discovery of novel functional microphase separated self-healing supramolecular architectures, illustrating dynamic and self-healing properties with an almost complete recovery of the initial mechanical performances healing within 24h at 30 °C. Collectively, our studies prove that phase segregation in H-bonding polymers is an important principle, capable to generate nanostructures and dynamic properties not achieved in covalently linked polymers. The results discussed illustrate that a rational architectural design within H-bonding polymer systems in interplay with phase segregation in both the amorphous and crystalline state opens perspectives to develop artificial supramolecular systems approaching the level of complexities and properties present in nature’s biomaterials.
The metal catalyzed azide/alkyne ‘click’ reaction (a variation of the Huisgen 1,3‐dipolar cycloaddition reaction between terminal acetylenes and azides) has vastly increased in broadness and ...application in the field of polymer science. Thus, this reaction represents one of the few universal, highly efficient functionalization reactions, which combines both high efficiency with an enormously high tolerance of functional groups and solvents under highly moderate reaction temperatures (25–70 °C). The present review assembles an update of this reaction in the field of polymer science (linear polymers, surfaces) with a focus on the synthesis of functionalized polymeric architectures and surfaces.
The modification of polymers after the successful achievement of a polymerization process represents an important task in macromolecular science. Cycloaddition reactions, among them the metal ...catalyzed azide/alkyne ‘click’ reaction (a variation of the Huisgen 1,3‐dipolar cycloaddition reaction between terminal acetylenes and azides) represents an important contribution towards this endeavor. They combine high efficiency (usually above 95%) with a high tolerance of functional groups and solvents, as well as moderate reaction temperatures (25–70 °C). The present review assembles recent literature for applications of this reaction in the field of polymer science (linear polymers, dendrimers, gels) as well as the use of this and related reactions for surface modification on carbon nanotubes, fullerenes, and on solid substrates, and includes the authors own publications in this field. A number of references (>100) are included.
The copper‐catalyzed azide/alkyne cycloaddition reaction (CuAAC) has emerged as the most useful “click” chemistry. Polymer science has profited enormously from CuAAC by its simplicity, ease, scope, ...applicability and efficiency. Basic principles of the CuAAC are reviewed with a focus on homogeneous and heterogeneous catalysts, ligands, anchimeric assistance, and basic chemical principles. Recent developments of ligand design and acceleration are discussed.
Copper‐I‐catalyzed “click” chemistry (CuAAC) has emerged as the most broadly useful click chemistry and has been widely applied in material science, bioorganic chemistry, and macromolecular chemistry. External additives and parameters (homogeneous/heterogeneous catalysts, ligands, anchimeric assistance, and basic chemical principles) are discussed, stressing polymer science's profit from CuAAC's complex chemistry, which allows for low Cu content in the final products.
Self-Healing Polymers via Supramolecular Forces Herbst, Florian; Döhler, Diana; Michael, Philipp ...
Macromolecular rapid communications.,
February 12, 2013, Letnik:
34, Številka:
3
Journal Article
Recenzirano
As polymers and polymeric materials are “the” smart invention and technological driving force of the 20th century, the quest for self‐healing or self‐repairing polymers is strong. The concept of ...supramolecular self‐healing materials relies on the use of noncovalent, transient bonds to generate networks, which are able to heal the damaged site, putting aspects of reversibility and dynamics of a network as crucial factors for the understanding and design of such self‐healing materials. This Review describes recent examples and concepts of supramolecular polymers based on hydrogen bonding, π–π interactions, ionomers, and coordinative bonds, thus convincingly discussing the advantages and versatility of these supramolecular forces for the design and realization of self‐healing polymers.
This Review describes the concepts of supramolecular polymers with multiple self‐healing properties while utilizing the dynamic and reversible character of hydrogen bonds, π–π interactions, ionomers, and coordinative bonds. Furthermore, the versatility of these reversible dynamic forces and their great challenges for the design of self‐healing polymers are discussed for various examples.
Conspectus Click chemistry has emerged as a significant tool for materials science, organic chemistry, and bioscience. Based on the initial concept of Barry Sharpless in 2001, the ...copper(I)-catalyzed azide/alkyne cycloaddition (CuAAC) reaction has triggered a plethora of chemical concepts for linking molecules and building blocks under ambient conditions, forming the basis for applications in autonomous cross-linking materials. Self-healing systems on the other hand are often based on mild cross-linking chemistries that are able to react either autonomously or upon an external trigger. In the ideal case, self-healing takes place efficiently at low temperatures, independent of the substrate(s) used, by forming strong and stable networks, binding to the newly generated (cracked) interfaces to restore the original material properties. The use of the CuAAC in self-healing systems, most of all the careful design of copper-based catalysts linked to additives as well as the chemical diversity of substrates, has led to an enormous potential of applications of this singular reaction. The implementation of click-based strategies in self-healing systems therefore is highly attractive, as here chemical (and physical) concepts of molecular reactivity, molecular design, and even metal catalysis are connected to aspects of materials science. In this Account, we will show how CuAAC reactions of multivalent components can be used as a tool for self-healing materials, achieving cross-linking at low temperatures (exploiting concepts of autocatalysis or internal chelation within the bulk CuAAC and systematic optimization of the efficiency of the used Cu(I) catalysts). Encapsulation strategies to separate the click components by micro- and nanoencapsulation are required in this context. Consequently, the examples reported here describe chemical concepts to realize more efficient and faster click reactions in self-healing polymeric materials. Thus, enhanced chain diffusion in (hyper)branched polymers, autocatalysis, or internal chelation concepts enable efficient click cross-linking already at 5 °C with a simultaneously reduced amount of Cu(I) catalyst and increased reaction rates, culminating in the first reported self-healing system based on click cycloaddition reactions. Via tailor-made nanocarbon/Cu(I) catalysts we can further improve the click cross-linking reaction in view of efficiency and kinetics, leading to the generation of self-healing graphene-based epoxy nanocomposites. Additionally, we have designed special CuAAC click methods for chemical reporting and visualization systems based on the detection of ruptured capsules via a fluorogenic click reaction, which can be combined with CuAAC cross-linking reactions to obtain simultaneous stress detection and self-healing within polymeric materials. In a similar concept, we have prepared polymeric Cu(I)–biscarbene complexes to detect (mechanical) stress within self-healing polymeric materials via a triggered fluorogenic reaction, thus using a destructive force for a constructive chemical response.
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