Ultrasound induced formation of organogel from a glutamic dendron

Unnatural Amino Acid: 4-Aminopyrazolonyl Amino Acid Comprising Tri-Peptides Forms Organogel With Co-Solvent (EtOAc:Hexane)

Ampyrone is an amino-functionalized heterocyclic pyrazolone derivative that possesses therapeutic values such as analgesic, anti-inflammatory, and antipyretics. The chemical structure of ampyrone exhibits excellent hydrogen bonding sites and is considered as the potential scaffold of supramolecular self-assembly. Recently, this molecule has been derived into unnatural amino acids such as aminopyrazolone amino acid and its peptides. This report describes that one of its amino acids, O-alkylated ampyrone, containing hybrid (α/β) peptides forms organogel after sonication at 50–55°C with 0.7–0.9% (w/v) in ethyl acetate: hexane (1:3). The formation/morphology of such organogels is studied by nuclear magnetic resonance Fourier-transform infrared (FT-IR), circular dichroism (CD), scanning electron microscope (SEM), transmission electron microscopy (TEM), powder X-ray diffraction (Powder-XRD), and thermogravimetric analysis (TGA). Energy-minimized conformation of APA-peptides reveals the possibility of intermolecular hydrogen bonding. Hence, APA-peptides are promising peptidomimetics for the organogel-peptides.

A tertiary amine group-based organogelator with pH-trigger recyclable property

The separation and recovery of oils and organogelators can be easily realized by tuning the pH value.

Structure–property relationship of novel supramolecular gels based on coumarins

LMWGs based on coumarins could form supramolecular gels with unusual mechanical properties explained by its interactions at theoretical level.

Self-assembly and multifunctionality of peptide organogels: oil spill recovery, dye absorption and synthesis of conducting biomaterials

The self-assembly of a series of low molecular weight gelator dipeptides containing para amino benzoic acid has been studied in mechanistic detail. All four dipeptides form phase selective, thermoreversible, rigid gels in a large range of organic solvents and fuels such as petrol, diesel, and kerosene. The mechanism of self-assembly has been dissected in detail using several experimental techniques. Self-assembly is driven mainly by aromatic and hydrophobic interactions. Hydrogen bonding groups, though present, seem to make a trivial contribution towards the self-assembly process. Phase selective gelation abilities in fuels in the presence of acidic, basic and saline conditions, together with the easy recovery of fuels from the organogels, render the peptides potential candidates for addressing oil-spill recovery. Being electron rich systems, these organogelators can absorb cationic dyes with >90% efficiency from wastewater. Finally, conducting biomaterials have been synthesized by the insertion of reduced graphene oxide into the organogels. Such small peptide based gelator molecules, being economically viable and easy to prepare, in addition to being multifunctional, are a hot area of research in the field of materials chemistry.

The self-assembly of a series of low molecular weight gelator dipeptides containing para amino benzoic acid has been studied in mechanistic detail.

Designer Peptide and Protein Dendrimers: A Cross-Sectional Analysis

Dendrimers have attracted immense interest in science and technology due to their unique chemical structure that offers a myriad of opportunities for researchers. Dendritic design allows us to present peptides in a branched three-dimensional fashion that eventually leads to a globular shape, thus mimicking globular proteins. Peptide dendrimers, unlike other classes of dendrimers, have immense applications in biomedical research due to their biological origin. The diversity of potential building blocks and innumerable possibilities for design, along with the fact that the area is relatively underexplored, make peptide dendrimers sought-after candidates for various applications. This review summarizes the stepwise evolution of peptidic dendrimers along with their multifaceted applications in various fields. Further, the introduction of biomacromolecules such as proteins to a dendritic scaffold, resulting in complex macromolecules with discrete molecular weights, is an altogether new addition to the area of organic chemistry. The synthesis of highly complex and fully folded biomacromolecules on a dendritic scaffold requires expertise in synthetic organic chemistry and biology. Presently, there are only a handful of examples of protein dendrimers; we believe that these limited examples will fuel further research in this area.

A hydrogel directly assembled from a copper metal–organic polyhedron for antimicrobial application

A hydrogel was directly assembled from a Cu-MOP by a facile procedure without adding any polymers for the first time, and it exhibited excellent antibacterial activity towards both Gram-negative and Gram-positive bacteria.

Ultrasound-induced gelation of a giant macrocycle

A 68-membered macrocycle undergoes ultrasound-induced supramolecular gelation in acetonitrile. The sonogel shows a remarkable thermostability, indicating that self-assembly is mediated by exceptionally robust non-covalent interactions. Model compounds indicate that the macrocyclic topology is essential for gelation to occur.

Achiral non-fluorescent molecule assisted enhancement of circularly polarized luminescence in naphthalene substituted histidine organogels

A naphthalene substituted histidine derivative was found to form an organogel showing circularly polarized luminescence (CPL) and the addition of non-fluorescent achiral benzoic acids could efficiently enhance the CPLvianon-covalent interactions.

Self-Assembly and Drug Release Capacities of Organogels via Some Amide Compounds with Aromatic Substituent Headgroups

In this work, some amide compounds with different aromatic substituent headgroups were synthesized and their gelation self-assembly behaviors in 22 solvents were characterized as new gelators. The obtained results indicated that the size of aromatic substituent headgroups in molecular skeletons in gelators showed crucial effect in the gel formation and self-assembly behavior of all compounds in the solvents used. Larger aromatic headgroups in molecular structures in the synthesized gelator molecules are helpful to form various gel nanostructures. Morphological investigations showed that the gelator molecules can self-assembly and stack into various organized aggregates with solvent change, such as wrinkle, belt, rod, and lamella-like structures. Spectral characterizations suggested that there existed various weak interactions including π-π stacking, hydrogen bonding, and hydrophobic forces due to aromatic substituent headgroups and alkyl substituent chains in molecular structures. In addition, the drug release capacities experiments demonstrated that the drug release rate in present obtained gels can be tuned by adjusting the concentrations of dye. The present work would open up enormous insight to design and investigate new kind of soft materials with designed molecular structures and tunable drug release performance.

Fluorous 'ponytails' lead to strong gelators showing thermally induced structure evolution

Appending perfluoroalkyl substituents to bis(urea) gelators results in significantly decreased inter-chain interactions with markedly thinner fibres and hence more cross-linked and more transparent gels with potential applications in the crystallisation of fluorinated pharmaceuticals. Gel structure has been probed by detailed SANS measurements which indicate a surprising structure evolution on thermal cycling, not seen for hydrocarbon analogues. The SANS data are complemented by the single crystal X-ray structure of one fluorinated gelator.

Self-Assembly and Nanostructures in Organogels Based on a Bolaform Cholesteryl Imide Compound with Conjugated Aromatic Spacer

The self-assembly of small functional molecules into supramolecular structures is a powerful approach toward the development of new nanoscale materials and devices. As a class of self-assembled materials, low weight molecular organic gelators, organized in special nanoarchitectures through specific non-covalent interactions, has become one of the hot topics in soft matter research due to their scientific values and many potential applications. Here, a bolaform cholesteryl imide compound with conjugated aromatic spacer was designed and synthesized. The gelation behaviors in 23 solvents were investigated as efficient low-molecular-mass organic gelator. The experimental results indicated that the morphologies and assembly modes of as-formed organogels can be regulated by changing the kinds of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecule self-assemble into different aggregates, from wrinkle and belt to fiber with the change of solvents. Spectral studies indicated that there existed different H-bond formations between imide groups and assembly modes. Finally, some rational assembly modes in organogels were proposed and discussed. The present work may give some insight to the design and character of new organogelators and soft materials with special structures.

Spacer effect on nanostructures and self-assembly in organogels via some bolaform cholesteryl imide derivatives with different spacers

In this paper, new bolaform cholesteryl imide derivatives with different spacers were designed and synthesized. Their gelation behaviors in 23 solvents were investigated, and some of them were found to be low molecular mass organic gelators. The experimental results indicated that these as-formed organogels can be regulated by changing the flexible/rigid segments in spacers and organic solvents. Suitable combination of flexible/rigid segments in molecular spacers in the present cholesteryl gelators is favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle and belt to fiber with the change of spacers and solvents. Spectral studies indicated that there existed different H-bond formations between imide groups and assembly modes, depending on the substituent spacers in molecular skeletons. The present work may give some insight into the design and character of new organogelators and soft materials with special molecular structures.

Self-assembly of organogels via new luminol imide derivatives: diverse nanostructures and substituent chain effect

Luminol is considered as an efficient sycpstem in electrochemiluminescence (ECL) measurements for the detection of hydrogen peroxide. In this paper, new luminol imide derivatives with different alkyl substituent chains were designed and synthesized. Their gelation behaviors in 26 solvents were tested as novel low molecular mass organic gelators. It was shown that the length and number of alkyl substituent chains linked to a benzene ring in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. Longer alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. Scanning electron microscope and atomic force microscope observations revealed that the gelator molecules self-assemble into different micro/nanoscale aggregates from a dot, flower, belt, rod, and lamella to wrinkle with change of solvents. Spectral studies indicated that there existed different H-bond formations and hydrophobic forces, depending on the alkyl substituent chains in molecular skeletons. The present work may give some insight to the design and characteristic of new versatile soft materials and potential ECL biosensors with special molecular structures.

Regulation of substituent groups on morphologies and self-assembly of organogels based on some azobenzene imide derivatives

In this paper, new azobenzene imide derivatives with different substituent groups were designed and synthesized. Their gelation behaviors in 21 solvents were tested as novel low-molecular-mass organic gelators. It was shown that the alkyl substituent chains and headgroups of azobenzene residues in gelators played a crucial role in the gelation behavior of all compounds in various organic solvents. More alkyl chains in molecular skeletons in present gelators are favorable for the gelation of organic solvents. Scanning electron microscopy and atomic force microscopy observations revealed that the gelator molecules self-assemble into different aggregates, from wrinkle, lamella, and belt to fiber with the change of solvents. Spectral studies indicated that there existed different H-bond formations between amide groups and conformations of methyl chains. The present work may give some insight to the design and character of new organogelators and soft materials with special molecular structures.

High-frequency ultrasound-responsive block copolymer micelle

Micelles of a diblock copolymer composed of poly(ethylene oxide) and poly(2-tetrahydropyranyl methacrylate) (PEO-b-PTHPMA) in aqueous solution could be disrupted by high-frequency ultrasound (1.1 MHz). It was found that, upon exposure to a high-intensity focused ultrasound (HIFU) beam at room temperature, the pH value of the micellar solution decreased over irradiation time. The infrared spectroscopic analysis of solid block copolymer samples collected from the ultrasound irradiated micellar solution revealed the formation of carboxylic acid dimers and hydroxyl groups. These characterization results suggest that the high-frequency HIFU beam could induce the hydrolysis reaction of THPMA at room temperature resulting in the cleavage of THP groups. The disruption of PEO-b-PTHPMA micelles by ultrasound was investigated by using dynamic light scattering, atomic force microscopy, and fluorescence spectroscopy. On the basis of the pH change, it was found that the disruption process was determined by a number of factors such as the ultrasound power, the micellar solution volume and the location of the focal spot of the ultrasound beam. This study shows the potential to develop ultrasound-sensitive block copolymer micelles by having labile chemical bonds in the polymer structure, and to use the high-frequency HIFU to trigger a chemical reaction for the disruption of micelles.

Stable oil-in-water emulsions prepared from soy protein-dextran conjugates

The solubility of acid soluble soy protein (ASSP) is poor in the pH range of 4-7. ASSP-dextran conjugates were prepared through the Maillard reaction to increase the solubility and/or dispersibility of ASSP. By using the conjugates and ultrasonication emulsification, stable oil-in-water emulsions with submicrometer-sized droplets were obtained. The factors, such as ASSP conjugation degree, that influence the emulsion stability were investigated. The emulsions were characterized using dynamic light scattering, zeta-potential, and atomic force microscopy. In the ultrasonication process, the increases of surface activity and aggregation of protein result in the formation of stable oil-water interface films. The dextran molecules conjugated to the protein effectively enhance the hydrophilicity and steric repulsion of the oil droplets, and therefore the emulsions are stable against heat treatment, long-term storage, and changes of pH and ionic strength. It was further verified that using protein-polysaccharide conjugates and ultrasonication emulsification is a versatile method for preparing stable emulsions.

Metal ion and anion-based "tuning" of a supramolecular metallogel

A bis(pyridylurea) ligand (1) forms metallogels in methanol in the presence of up to 0.5 equiv of copper(II) chloride. The metallogel has been characterized using powder X-ray diffraction, SEM, and MAS NMR spectroscopic techniques. The addition of further copper(II) chloride gives the unusual crystalline 4:3 coordination polymer [Cu3(1)4Cl4]Cl2 x nH2O (2). In the presence of 0.5 equiv of copper(II) nitrate, the 2:1 crystalline coordination polymer [Cu(1)2](NO3)2 x H2O x MeOH (5) is isolated. Both 2 and 5 have been characterized by single-crystal X-ray diffraction. Complex 5 represents a possible model for the gelator and highlights key interactions with counteranions that suggest a means to tune gel properties using anion binding. The influence of chloride and acetate anions (as their NBu4+ salts) on the rheological properties of the copper(II) chloride metallogels of 1 are investigated. The rheology of the anion-containing mixtures shows complex behavior with the gel structure apparently evolving over time.

Design and self-assembly of L-glutamate-based aromatic dendrons as ambidextrous gelators of water and organic solvents

A series of L-glutamate-based dendrons containing aromatic cores ranging from phenyl to naphthyl to anthryl were synthesized, and their self-assembly in organic solvents as well as in water was investigated. It was found that all of these dendrons formed organogels with hexane and simultaneously formed the hydrogels with water, thus exhibiting ambidextrous properties. Nanofiber structures are essentially formed in organogels and hydrogels, and some nanostrips are formed in some of the hydrogels. During gel formation, both hydrogen bonds between the amide groups and the pi-pi stacking between the aromatic rings played a predominant role in forming the ID nanostructures. Both the hydrogels and the organogels containing naphthyl and anthryl groups showed fluorescence emission. In comparison with the corresponding compounds in solution, the naphthyl-containing dendrons showed a strong enhancement of fluorescence in the gel. In the case of anthryl-containing dendrons, fluorescence enhancement was observed for the derivative with anthryl substituted at the 9 position, whereas a decrease was observed for the gels of the 2-substituted derivative. Although the chirality of L-glutamate could not be transferred to the aromatic chromophores in solution, it was transferred to the chromophores in gels as a result of the self-assembly and strong pi-pi interaction of the gelators. On the basis of the properties of the organogels and hydrogels, a thermally driven chiroptical switch was proposed. That is, the chirality disappeared when the gel was heated to solution, whereas it returned when cooled to a gel. The process can be repeated many times.