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1. Supramolecular spheres assembled from covalent and supramolecular dendritic crowns dictate the supramolecular orientational memory effect mediated by Frank–Kasper phases

   https://doi.org/10.1016/j.giant.2020.100001  

   Huang, Ning; Imam, Mohammad R.; Sienkowska, Monika J.; Peterca, Mihai; Holerca, Marian N.; Wilson, Daniela A.; Rosen, Brad M.; Partridge, Benjamin E.; Xiao, Qi; Percec, Virgil (March 2020, Giant)

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2. Dynamics in supramolecular nanomaterials

   https://doi.org/10.1039/d1sm00047k  

   Cho, Yukio; Christoff-Tempesta, Ty; Kaser, Samuel J.; Ortony, Julia H. (June 2021, Soft Matter)

   Self-assembly of amphiphilic small molecules in water leads to nanostructures with customizable structure–property relationships arising from their tunable chemistries. Characterization of these assemblies is generally limited to their static structures – e.g. their geometries and dimensions – but the implementation of tools that provide a deeper understanding of molecular motions has recently emerged. Here, we summarize recent reports showcasing dynamics characterization tools and their application to small molecule assemblies, and we go on to highlight supramolecular systems whose properties are substantially affected by their conformational, exchange, and water dynamics. This review illustrates the importance of considering dynamics in rational amphiphile design. 

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3. Temperature-responsive supramolecular hydrogels

   https://doi.org/10.1039/D0TB01814G  

   Xian, Sijie; Webber, Matthew J. (October 2020, Journal of Materials Chemistry B)

   null (Ed.)

   Hydrogels comprise a class of soft materials which are extremely useful in a number of contexts, for example as matrix-mimetic biomaterials for applications in regenerative medicine and drug delivery. One particular subclass of hydrogels consists of materials prepared through non-covalent physical crosslinking afforded by supramolecular recognition motifs. The dynamic, reversible, and equilibrium-governed features of these molecular-scale motifs often transcend length-scales to endow the resulting hydrogels with these same properties on the bulk scale. In efforts to engineer hydrogels of all types with more precise or application-specific uses, inclusion of stimuli-responsive sol–gel transformations has been broadly explored. In the context of biomedical uses, temperature is an interesting stimulus which has been the focus of numerous hydrogel designs, supramolecular or otherwise. Most supramolecular motifs are inherently temperature-sensitive, with elevated temperatures commonly disfavoring motif formation and/or accelerating its dissociation. In addition, supramolecular motifs have also been incorporated for physical crosslinking in conjunction with polymeric or macromeric building blocks which themselves exhibit temperature-responsive changes to their properties. Through molecular-scale engineering of supramolecular recognition, and selection of a particular motif or polymeric/macromeric backbone, it is thus possible to devise a number of supramolecular hydrogel materials to empower a variety of future biomedical applications. 

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4. Gradient supramolecular interactions and tunable mechanics in polychaete jaw inspired supramolecular interpenetrating networks

   https://doi.org/10.1016/j.europolymj.2019.04.015  

   Chase B. Thompson, Sourave Chatterjee (July 2019, European polymer journal)

   Polychaete worms display a remarkable jaw structure, where a gradient in metal-ligand coordination down thelength of the jaw results in a shift from hard to soft mechanics. To mimic these gradient structures, a Zn-coordinated supramolecular polymer is crosslinked into a covalent matrix to afford supramolecular semi-in-terpenetrating networks (SIPNs). These SIPN materials exhibit improved mechanics with a lower supramolecularcontent (30 wt%), allowing for energy dissipation through cavitation to increase material toughness. The shift inmechanical behavior is further attributed to the morphology, where the size of the phase-separated droplets andnature of the continuous phase in these SIPNs contributes to the material mechanics. Furthermore, chemicalgradients are applied to these systems through exposure to a competitive ligand, offering control over the lo-calization of supramolecular interactions. These materials offer a framework to mediate mechanics whilemaintaining the ability to program gradient supramolecular interactions. 

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5. Layered supramolecular hydrogels from thioglycosides

   https://doi.org/10.1039/d2tb00037g  

   Wang, Yu-Cheng; Kegel, Laurel L.; Knoff, David S.; Deodhar, Bhushan S.; Astashkin, Andrei V.; Kim, Minkyu; Pemberton, Jeanne E. (April 2022, Journal of Materials Chemistry B)

   Low molecular weight hydrogels are made of small molecules that aggregate via noncovalent interactions. Here, comprehensive characterization of the physical and chemical properties of hydrogels made from thioglycolipids of the disaccharides lactose and cellobiose with simple alkyl chains is reported. While thiolactoside hydrogels are robust, thiocellobioside gels are metastable, precipitating over time into fibrous crystals that can be entangled to create pseudo-hydrogels. Rheology confirms the viscoelastic solid nature of these hydrogels with storage moduli ranging from 10–600 kPa. Additionally, thiolactoside hydrogels are thixotropic which is a desirable property for many potential applications. Freeze-fracture electron microscopy of xerogels shows layers of stacked sheets that are entangled into networks. These structures are unique compared to the fibers or ribbons typically reported for hydrogels. Differential scanning calorimetry provides gel-to-liquid phase transition temperatures ranging from 30 to 80 °C. Prodan fluorescence spectroscopy allows assignment of phase transitions in the gels and other lyotropic phases of high concentration samples. Phase diagrams are estimated for all hydrogels at 1–10 wt% from 5 to ≥ 80 °C. These hydrogels represent a series of interesting materials with unique properties that make them attractive for numerous potential applications. 

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