Ionogels of Sugar Surfactant in Ethylammonium Nitrate: Phase Transition from Closely Packed Bilayers to Right-Handed Twisted Ribbons

In the simplest ionic liquid, ethylammonium nitrate (EAN), ionogels with high mechanical strength were prepared from a surfactant with a disaccharide polar head. Phase structures from closely packed bilayers to right-handed twisted ribbons were determined via freeze-fracture transmission electron microscopy (FF-TEM) observations. The phase transition mechanism was investigated deeply and systematically. The temperature contributes to suitable tail chain conformations of surfactant molecules for adapting to different self-assembled structures including right-handed twisted ribbons and bilayers. Two different arrays were revealed for different bilayers by the small-angle X-ray scattering (SAXS) measurements. The rheological and tribological properties of the ionogels were investigated. The better lubricating property and antiwear capability of the ionogels compared to the EAN may be attributed to the structure characteristics and the good thixotropic properties

Magnetic-Field-Induced Orientational Phase Structure Transition

Magnetic field effect on the phase transition at high temperature (from 50 °C) inside the magnetic field has been found in C₁₄G₂ (<i>N</i>-tetradecyllactobionamide)/C₁₂EO₄ (tetraethylene glycol monododecyl ether)/D₂O system. The phase was transited quickly from lamellar phase to isotropic phases [bottom, micellar phase (L₁ phase) and top, sponge phase (L₃ phase)] induced by a magnetic field, which was demonstrated by ²H NMR and FF-TEM measurements. The isotropic phases induced by magnetic field were not stable, and the upper L₃ phase can recover to lamellar phase after being restored in a 55 °C thermostat outside the magnetic field for about one month. During the mechanism study, the C₁₂EO₄ molecule was proved to be the dominant component for the phase transition induced by the magnetic field, while the C₁₄G₂ molecule was the auxiliary and just affected the transition speed. The breaking and rebuilding of hydrogen bonds could play an important role in the phase transition and recovering. Moreover, the surfactant concentration had an effect on the speed of phase transiting and phase recovering. These observations could provide an understanding of the phase transition and also the applications for the controlled drug delivery system of bilayer membranes driving, induced by the magnetic field

Colloidal Wormlike Micelles with Highly Ferromagnetic Properties

For the first time, a new fabrication method for manipulating the ferromagnetic property of molecular magnets by forming wormlike micelles in magnetic-ionic-liquid (mag-IL) complexes is reported. The ferromagnetism of the mag-IL complexes was enhanced 4-fold because of the formation of wormlike micelles, presenting new evidence for the essence of magnetism generation at a molecular level. Characteristics such as morphology and magnetic properties of the wormlike micelle gel were investigated in detail by cryogenic transmission electron microscopy (Cryo-TEM), rheological measurements, circular dichroism (CD), FT-IR spectra, and the superconducting quantum interference device method (SQUID). An explanation of ferromagnetism elevation from the view of the molecular (ionic) distribution is also given. For the changes of magnetic properties (ferromagnetism elevation) in the wormlike micelle systems, the ability of CTAFe in magnetizing AzoNa₄ (or AzoH₄) can be ascribed to an interplay of the magnetic [FeCl₃Br]⁻ ions both in the Stern layer and in the cores of the wormlike micelles. Formation of colloidal aggregates, i.e., wormlike micelles, provides a new strategy to tune the magnetic properties of novel molecular magnets

Rapid-Forming and Self-Healing Agarose-Based Hydrogels for Tissue Adhesives and Potential Wound Dressings

To meet the progressive requirements of advanced engineering materials with superior physicochemical performances, self-healing and injectable hydrogels (AD hydrogels) based on agarose with pH-response were prepared through dynamic covalent Schiff-base linkages by simply mixing nontoxic agarose–ethylenediamine conjugate (AG-NH₂) and dialdehyde-functionalized polyethylene glycol (DF-PEG) solutions. The self-healing and injectable capabilities of the hydrogels without any external stimulus are ascribed to dynamic covalent Schiff-base linkages between the aldehyde groups of DF-PEG and amine groups on AG-NH₂ backbone. It is demonstrated that the AD hydrogels possess interconnected porous morphologies, rapid gelation time, excellent deformability, and good mechanical strength. The incorporated Schiff’s base imparts the hydrogels to the remarkable tissue adhesiveness. In vivo hemostatic tests on rabbit liver demonstrate that the hydrogels are able to stanch the severe trauma effectively. Compared with the conventional gauze treatment, the total amount of bleeding sharply declined to be (0.19 ± 0.03) g, and hemostasis time was strikingly shorter than 10 s after treating with AD hydrogels. In summary, the self-healing ability, cytocompatibility, and adhesion characteristic of the pH-responsive hydrogels make them promising candidates for long-lived wound dressings in critical situations

Room-Temperature Super Hydrogel as Dye Adsorption Agent

Supramolecular hydrogels were prepared in the mixtures of a chiral amphiphilic lithocholic acid (LCA) and a nonionic surfactant, dodecyldimethylamine oxide (C₁₂DMAO), in water. With the addition of LCA to C₁₂DMAO micellar solutions, a transition from micelles to gels occurs at room temperature. Hydrogels can form at very low concentrations (below 0.1 wt %), exhibiting a super gelation capability. The rheological measurements show a strong mechanical strength with an elastic modulus exceeding 5000 Pa and a yield stress exceeding 100 Pa. Microstructures determined by TEM, SEM, and AFM observations demonstrate that the gels are formed by intertwined helical fibrils. The formation of fibrils is induced by enormous cycles of units composed of two LCA molecules and four C₁₂DMAO molecules driven by comprehensive noncovalent interaction, especially the hydrogen bonds produced in two reversed LCA molecules and the C₁₂DMAOH⁺–C₁₂DMAO pairs. The xerogels show excellent adsorption capability of the toxic dye with a maximum adsorption value of 202 mg·g^–1

Rapid-Forming and Self-Healing Agarose-Based Hydrogels for Tissue Adhesives and Potential Wound Dressings

To meet the progressive requirements of advanced engineering materials with superior physicochemical performances, self-healing and injectable hydrogels (AD hydrogels) based on agarose with pH-response were prepared through dynamic covalent Schiff-base linkages by simply mixing nontoxic agarose–ethylenediamine conjugate (AG-NH₂) and dialdehyde-functionalized polyethylene glycol (DF-PEG) solutions. The self-healing and injectable capabilities of the hydrogels without any external stimulus are ascribed to dynamic covalent Schiff-base linkages between the aldehyde groups of DF-PEG and amine groups on AG-NH₂ backbone. It is demonstrated that the AD hydrogels possess interconnected porous morphologies, rapid gelation time, excellent deformability, and good mechanical strength. The incorporated Schiff’s base imparts the hydrogels to the remarkable tissue adhesiveness. In vivo hemostatic tests on rabbit liver demonstrate that the hydrogels are able to stanch the severe trauma effectively. Compared with the conventional gauze treatment, the total amount of bleeding sharply declined to be (0.19 ± 0.03) g, and hemostasis time was strikingly shorter than 10 s after treating with AD hydrogels. In summary, the self-healing ability, cytocompatibility, and adhesion characteristic of the pH-responsive hydrogels make them promising candidates for long-lived wound dressings in critical situations

Au NP Honeycomb-Patterned Films with Controllable Pore Size and Their Surface-Enhanced Raman Scattering

Honeycomb-patterned films (HPFs) of Au nanoparticles (Au NPs) with pore size controlled by varying the quantity of Au NPs or using modified agents of different mercaptans (C₁₄H₂₉SH, C₁₆H₃₃SH, and C₁₈H₃₇SH) were prepared. The strength of the HPFs containing Au NPs can be enhanced because of the addition of polymers including polystyrene, poly­(l-lactic acid), and poly­(methyl methacrylate-<i>co</i>-ethyl acrylate). With an increase in the amount of polymer and the number of Au NPs or the chain length of the modified agents, the pore size of HPFs decreases, indicating that the pore size can be well controlled by adjusting the above factors. Interestingly, HPFs with elliptical pores that were created by the direction of the air flow were observed. The pore diameter on the outer rim is smaller than that in the center, which should be because of the subordinate evaporation of the solvent in the center. Sponge structures were observed in the cross sections of the walls of HPFs, which should be produced by microphase separation. The HPFs consisting of Au NPs with controllable pore size exhibited stronger surface-enhanced Raman scattering. We believe that the HPFs composed of metal NPs such as Au, Ag, and Cu are exploited in multispectral scanners, nanophotons, and sensors

Porphyrin-Based Honeycomb Films and Their Antibacterial Activity

Micrometer-sized porous honeycomb-patterned thin films based on hybrid complexes formed via electrostatic interaction between Mn­(III) meso-tetra­(4-sulfonatophenyl) porphine chloride (an acid form, {MnTPPS}) and dimethyldioctadecylammonium bromide (DODMABr). The morphology of the microporous thin films can be well regulated by controlling the concentration of MnTPPS-DODMA complexes, DODMABr, and polystyrene (PS), respectively. The formation of the microporous thin films was largely influenced by different solvents. The well-ordered microporous films of MnTPPS-DODMA complexes exhibit a more efficient antibacterial activity under visible light than those of hybrid complexes of nanoparticles modified with DODMABr, implying that well-ordered microporous films containing porphyrin composition can improve photochemical activity and more dominance in applications in biological medicine fields

First Fluorinated Zwitterionic Micelle with Unusually Slow Exchange in an Ionic Liquid

The micellization of a fluorinated zwitterionic surfactant in ethylammonium nitrate (EAN) was investigated. The freeze-fracture transmission electron microscope (FF-TEM) observations confirm the formation of spherical micelles with the average diameter 25.45 ± 3.74 nm. The micellization is an entropy-driven process at low temperature but an enthalpy-driven process at high temperature. Two sets of ¹⁹F NMR signals above the critical micelle concentration (cmc) indicate that the unusually slow exchange between micelles and monomers exists in ionic liquid; meanwhile, surfactant molecules are more inclined to stay in micelle states instead of monomer states at higher concentration. Through the analysis of the half line width (Δν_1/2), we can obtain the kinetic information of fluorinated zwitterionic micellization in an ionic liquid

Effect of Cationic Surfactants with Different Counterions on the Growth of Au Nanoclusters

The influence of a series of cationic surfactants composed of cetyltrimethylammonium cations with different counterions (Br^–, Cl^–, OH^–, C₇H₈O₃S^–, [CeCl₃Br]⁻, and NO₃^–) on the aging process of gold nanoclusters (Au NCs) was studied. The finely different points of Au NCs treated by different surfactants were demonstrated by UV–vis and fluorescence spectra, transmission electron microscopy images, etc. Because of the difference of counterions, these surfactants have diverse physicochemical properties in surface activity, specific conductivity, pH, and viscosity, which may account for the difference of Au NCs in the aging process. In addition, the affinity of the counterions in surfactants to the surface of Au has also been demonstrated completely. This affinity may further guide the difference of the synthesized Au nanomaterials