A ligand-chirality controlled supramolecular hydrogel (original) (raw)
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pH-Regulated supramolecular chirality of phenylalanine-based hydrogels
Materials Today Chemistry, 2019
To achieve desired physicochemical and biochemical activities of optically active molecules at targetted sites in biological systems, tuning of chiral sense by varying internal conditions (e.g., pH) is of utmost importance. However, it has been a challenge to gain the balance of non-covalent interactions required for chiral transformations merely by deviations in biochemical environment. Herein, pH-controlled chirality of supramolecular nanostructures obtained from coassembly of phenylalanine-derived gelator and achiral cationic polyacrylamide has successfully been achieved. Specifically, any changes in the pH remarkably influence the chirality of these nanostructures. For instance, coassembled hydrogels possessing L-enantiomer provide right-handed nanostructures at pH < 7; whereas at pH ! 7, handedness of nanostructures switches to the left-handed nanostructures. Moreover, viscoelastic properties and twist pitch were also regulated under the influence of pH change. This study may provide a methodology to control chirality by simply varying biochemical conditions, which points toward its potential to be used in biological systems as a key to gain preferential chiral sense in different sites of living systems.
Molecular recognition of achiral structural analogues, a remaining challenge for materials scientists and chemists , is the key to manipulating the applications and properties of supramolecular chiral materials. Herein, we report the molecular recognition of two harmful structural analogues i.e. melamine (MA) and cyanuric acid (CA) by using C 2-symmetric phenylalanine chiral hydrogelators. Two distinct molecular recognition events between hydrogelator fibrils and triazine based achiral molecules are demonstrated: phenylalanine-co-melamine (PF-coMA) gels showed chirality amplification while chirality inversion was observed for phenylalanine-co-cyanuric acid (PF-coCA) gels. Moreover, viscoelastic properties and twist pitch were also regulated under the influence of the achiral molecules. Such phenomenon is mainly mediated by H-bonding among the two components, which may subtly change the arrangement of the molecules, in turn, the self-assembled nanostructures. This method of using C 2-symmetric phenylalanine based gelators in the recognition of the achiral molecules may be broadly applicable for a wide variety of molecular recognition partners such as sugars.
European Journal of Organic Chemistry, 2015
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Controlled mechanical properties and supramolecular chirality of hydrogels via pH change
MethodsX, 2019
In order to widen the use of soft materials in tissue engineering and life sciences, hydrogels with improved mechanical properties and controlled chirality are critical to achieve. A methodology is presented to enhance the mechanical properties and gain the control of chirality of two component hydrogels by merely varying the solution pH. pH change has been used as a way to ionize the specific functionalities into positive and negative charges. These positive and negative charges are crucial to provide a surge of electrostatic interactions to the components, imparting the improvement in stability and regulating their optical activity. Our goal is to throw light on the significance of opposite charges in the hydrogels for achievement of desired properties. Role of ionisable groups is crucial to control viscoelastic and optical properties of supramolecular hydrogels. Increasing the pH of the solution increases the number of negative ions by affecting the ionisable moieties, which interact with the positive charges in the solution. Zeta potential of both materials has been analysed to ensure the presence of charged species.
Cation-Tuned Stimuli Responsive and Optical Properties of Supramolecular Hydrogels
Chemistry, an Asian journal, 2015
Hierarchical self-assembly of an amphiphilic tris-urea in aqueous media is shown. A mixture of the amphiphilic tris-urea and an alkaline solution gave a viscous solution composed of fibrous aggregates. This viscous solution transformed into supramolecular hydrogels, which are capable of hierarchically organizing into higher-order aggregates, in response to several cationic triggers. The resulting supramolecular hydrogels were relatively stiff and their storage moduli attained over 103 Pa. Stimuli responsive and optical properties of the resulting hydrogels were influenced by the cationic trigger. Proton and calcium ion triggers gave pH and chemical stimuli responsive hydrogels, respectively. A terbium ion trigger also provided a highly luminescent hydrogel through energy transfer from the tris-urea to terbium.
Nanomaterials
This perspective article shows new advances in the synthesis of colloids, gels, and aerogels generated by combining metal ions and ligands of biological interest, such as nucleobases, nucleotides, peptides, or amino acids, among other derivatives. The characteristic dynamism of coordination bonds between metal center and biocompatible-type ligands, together with molecular recognition capability of these ligands, are crucial to form colloids and gels. These supramolecular structures are generated by forming weak van der Waals bonds such as hydrogen bonds or π–π stacking between the aromatic rings. Most gels are made up of nano-sized fibrillar networks, although their morphologies can be tuned depending on the synthetic conditions. These new materials respond to different stimuli such as pH, stirring, pressure, temperature, the presence of solvents, among others. For these reasons, they can trap and release molecules or metal ions in a controlled way allowing their application in drug...
Binder driven self-assembly of metal-organic cubes towards functional hydrogels
Nature Communications
The process of assembling astutely designed, well-defined metal-organic cube (MOC) into hydrogel by using a suitable molecular binder is a promising method for preparing processable functional soft materials. Here, we demonstrate charge-assisted H-bonding driven hydrogel formation from Ga 3+-based anionic MOC ((Ga 8 (ImDC) 12) 12−) and molecular binders, like, ammonium ion (NH 4 +), N-(2-aminoethyl)-1,3-propanediamine, guanidine hydrochloride and β-alanine. The morphology of the resulting hydrogel depends upon the size, shape and geometry of the molecular binder. Hydrogel with NH 4 + shows nanotubular morphology with negative surface charge and is used for gel-chromatographic separation of cationic species from anionic counterparts. Furthermore, a photo-responsive luminescent hydrogel is prepared using a cationic tetraphenylethene-based molecular binder (DATPE), which is employed as a light harvesting antenna for tuning emission colour including pure white light. This photo-responsive hydrogel is utilized for writing and preparing flexible lightemitting display.
Ultrahigh-Water-Content Supramolecular Hydrogels Exhibiting Multistimuli Responsiveness
Journal of the American Chemical Society, 2012
Hydrogels are three-dimensional networked materials that are similar to soft biological tissues and have highly variable mechanical properties, making them increasingly important in a variety of biomedical and industrial applications. Herein we report the preparation of extremely high water content hydrogels (up to 99.7% water by weight) driven by strong host−guest complexation with cucurbit[8]uril (CB[8]). Cellulosic derivatives and commodity polymers such as poly(vinyl alcohol) were modified with strongly binding guests for CB[8] ternary complex formation (K eq = 10 12 M −2 ). When these polymers were mixed in the presence of CB[8], whereby the overall solid content was 90% cellulosic, a lightly colored, transparent hydrogel was formed instantaneously. The supramolecular nature of these hydrogels affords them with highly tunable mechanical properties, and the dynamics of the CB[8] ternary complex cross-links allows for rapid self-healing of the materials after damage caused by deformation. Moreover, these hydrogels display responsivity to a multitude of external stimuli, including temperature, chemical potential, and competing guests. These materials are easily processed, and the simplicity of their preparation, their availability from inexpensive renewable resources, and the tunability of their properties are distinguishing features for many important water-based applications.
Modulation of physical properties of supramolecular hydrogels based on a hydrophobic core
Physical chemistry chemical physics : PCCP, 2015
We demonstrate herein the variation in viscoelastic properties of supramolecular hydrogels (SMGs) composed of two amphiphiles, N-Palmitoyl-Gly-His (PalGH) and sodium palmitate (PalNa). PalGH molecules in water form lamellar-like assemblies, which stack into sheet-shaped aggregates, resulting in the evolution of three-dimensional network structures. Once PalNa is added to PalGH, the alkyl groups of PalNa incorporate themselves into the hydrophobic cores of PalGH lamellar-like assemblies, resulting in a change in the assembly from lamellar-like to fibrous micelle-like. Consequently, sheet-shaped aggregates turn into flexible fibrils, which form bundles, resulting in network structures. Mixed hydrogel network structures differ in morphology from those in homogenous PalGH and PalNa hydrogels. Changes in the network structure eventually alter the bulk viscoelastic properties of hydrogels. These results demonstrate that the viscoelastic properties of supramolecular hydrogels can be tuned ...
Journal of polymer science. Part A, Polymer chemistry, 2017
The success of exploiting cucurbit[n]uril (CB[n])-based molecular recognition in self-assembled systems has sparked a tremendous interest in polymer and materials chemistry. In this study, polymerization in the presence of host-guest complexes is applied as a modular synthetic approach toward a diverse set of CB[8]-based supramolecular hydrogels with desirable properties, such as mechanical strength, toughness, energy dissipation, self-healing, and shear-thinning. A range of vinyl monomers, including acrylamide-, acrylate-, and imidazolium-based hydrophilic monomers, could be easily incorporated as the polymer backbones, leading to a library of CB[8] hydrogel networks. This versatile strategy explores new horizons for the construction of supramolecular hydrogel networks and materials with emergent properties in wearable and self-healable electronic devices, sensors, and structural biomaterials. © 2017 The Authors. Journal of Polymer Science Part A: Polymer Chemistry Published by Wil...