Low molecular weight gels are formed by the self-assembly of small molecules into anisotropic structures that form a network capable of immobilizing the solvent. Such gels are common, with a huge ...number of different examples existing, and they have many applications. However, there are still significant gaps in our understanding of these systems and challenges that need to be addressed if we are to be able to fully design such systems. Here, a number of these challenges are discussed.
Supramolecular gels are formed by the self-assembly of small molecules under the influence of various non-covalent interactions. As the interactions are individually weak and reversible, it is ...possible to perturb the gels easily, which in turn enables fine tuning of their properties. Synthetic supramolecular gels are kinetically trapped and usually do not show time variable changes in material properties after formation. However, such materials potentially become switchable when exposed to external stimuli like temperature, pH, light, enzyme, redox, and chemical analytes resulting in reconfiguration of gel matrix into a different type of network. Such transformations allow gel-to-gel transitions while the changes in the molecular aggregation result in alteration of physical and chemical properties of the gel with time. Here, we discuss various methods that have been used to achieve gel-to-gel transitions by modifying a pre-formed gel material through external perturbation. We also describe methods that allow time-dependent autonomous switching of gels into different networks enabling synthesis of next generation functional materials. Dynamic modification of gels allows construction of an array of supramolecular gels with various properties from a single material which eventually extend the limit of applications of the gels. In some cases, gel-to-gel transitions lead to materials that cannot be accessed directly. Finally, we point out the necessity and possibility of further exploration of the field.
Stimuli responsive dynamic changes in the networks of self-assembled gels result in an alteration of physical and chemical properties of the gel with time.
Low molecular weight gelators (LMWG) self-assemble in solution into one-dimensional objects such as fibres or tapes. The entanglement of these fibres or tapes results in the formation of a network ...and a gel. In general, LMWG are investigated as single component systems. However, there are significant potential opportunities from mixed LMWG systems, which are rarely investigated. Here, we discuss the potential of multicomponent systems, and critically discuss the challenges.
We discuss the potential and challenges of multicomponent low molecular weight gels.
Low-molecular-weight gels are formed by the self-assembly of small molecules into fibrous networks that can immobilize a significant amount of solvent. Here, we focus on our work with a specific ...class of gelator, the functionalized dipeptide. We discuss the current state of the art in the area, focusing on how these materials can be controlled. We also highlight interesting and unusual observations and unanswered questions in the field.
The purpose of this paper is to encourage discussion among sport and recreation leaders in New Zealand about the need to engage futures thinking to adapt to a rapidly changing environment. The paper ...recognizes the generally risk adverse and conservative nature of the sport and recreation sector in New Zealand, the issue of 'presentism' and the paucity of international examples of futures thinking in sport and recreation, even though the landscape from within which it operates is rapidly evolving. Recognising the sport and recreation sector may not be fit for the future, the Government agency for Sport and Recreation commissioned a futures process, hosting workshops involving a diverse representation of the sport and recreation sector. The workshops explored drivers of change, assumptions, and alternative futures, including a preferred future and the actions needed to move toward it. Discussions reflected a desire to change, but a difficulty with knowing how to. Identification of alternative futures, assumption challenge and examining worldviews assisted with broadening thinking. Five characteristics of a preferred future emerged from discussions, representing choices and decisions about who New Zealanders are and want to be as a society. Working in partnership with Māori, empowering local decision-making, having a stronger relationship with the environment, building broader relationships, connections and networks, and building alignment around the preferred future were among the immediate actions the sport and recreation sector can take.
There is a real need for new antibiotics against self‐evolving bacteria. One option is to use biofriendly broad‐spectrum and mechanically tunable antimicrobial hydrogels that can combat ...multidrug‐resistant microbes. Whilst appealing, there are currently limited options. Herein, broad‐spectrum antimicrobial biometallohydrogels based on the self‐assembly and local mineralization of Ag+‐coordinated Fmoc‐amino acids are reported. Such biometallohydrogels have the advantages of localized delivery and sustained release, reduced drug dosage and toxicity yet improved bioavailability, prolonged drug effect, and tunable mechanical strength. Furthermore, they can directly interact with the cell walls and membrane, resulting in the detachment of the plasma membrane and leakage of the cytoplasm. This leads to cell death, triggering a significant antibacterial effect against both Gram‐negative (Escherichia coli) and Gram‐positive (Staphylococcus aureus) bacteria in cells and mice. This study paves the way for developing a multifunctional integration platform based on simple biomolecules coordinated self‐assembly toward a broad range of biomedical applications.
Broad‐spectrum antimicrobial biometallohydrogels based on Ag+‐coordinated Fmoc‐amino acids self‐assembly and local mineralization are presented. These biometallohydrogels have the advantages of reduced drug dosage and toxicity yet improved bioavailability, prolonged drug effect, and tunable mechanical strength. This study provides insights into the design and development of a multifunctional integration platform based on biomolecules coordinated self‐assembly toward a broad range of biomedical applications.
Low molecular weight gels, or supramolecular gels, are formed when small molecules self-assemble into fibrous structures. Above a critical concentration, the entanglement and cross-linking of these ...structures leads to the formation of a self-supporting gel. There are many examples where a single component is used to form such gels. There is however an ever-increasing interest in using multiple components. Here, if each component is able to form a gel by itself, a range of fibre types are possible, formed by either random or specific associations between the low molecular weight gelators (LMWG). The properties of the networks will depend on how the LMWG assemble into the primary fibrous structures and then how these primary structures entangle. As such, to understand these gels, it is necessary to understand the networks across multiple length scales. Here, we discuss the current state of the art, the effectiveness of the different techniques that have been used, and hopefully provide the impetus for the field to move away from the cartoon-level discussion of assembly.
We discuss the current state of characterising multicomponent low molecular weight gels across all length scales, and the effectiveness of the different techniques that have been used.
Nanoporous organic polymer networks Dawson, Robert; Cooper, Andrew I.; Adams, Dave J.
Progress in polymer science,
2012, Letnik:
37, Številka:
4
Journal Article
Recenzirano
Nanoporous organic polymer networks are a class of materials consisting solely of the lighter elements in the periodic table. These materials have potential uses in areas such as storage, separation, ...and catalysis. Here, we review the different classes of nanoporous polymer networks including covalent organic frameworks, hypercrosslinked polymers, conjugated microporous polymers, and polymers of intrinsic microporosity. The growing variety in synthetic routes to these materials allows a range of different polymer networks to be formed, including crystalline and amorphous structures. It is also possible to incorporate many different kinds of functional groups in a modular fashion. So far, most networks have been examined from the perspective of gas sorption, and this area is discussed critically and in depth in this review. The use of nanoporous organic polymers for applications such as catalysis and separations is an important developing area, and we discuss recent developments as well as highlighting potential future opportunities.
Dipeptide and tripeptide conjugates are receiving significant current interest as LMWG, driven by the accessibility of these materials, their relatively low cost and also the large number of examples ...that successfully form hydrogels. Their behaviour can easily modified by changes in the amino acids or the aromatic end groups chosen. The assembly process has been relatively well described for a small subset of these gelators, giving a good idea of the behaviour of these molecules and allowing an understanding of the conditions under which assembly will occur. Here, we critically review the literature in this area and consider the importance of gelator choice and method of assembly on the outcome of the gelation. We also discuss the applications of these hydrogels.
Hydrogels can be prepared by the triggered self‐assembly of dipeptide or tripeptide conjugates. Typically, the conjugates are di‐ or tripeptides functionalised at the N‐terminus with a Fmoc, naphthalene or pyrene moiety. Recent progress in the understanding of the design of these gelators as well as their applications is discussed.
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