Viscoelastic and Photoresponsive Properties of Microparticle/Liquid-Crystal Composite Gels: Tunable Mechanical Strength along with Rapid-Recovery Nature and Photochemical Surface Healing using an Azobenzene Dopant

We investigated viscoelastic and photoresponsive properties of the microparticle/liquid-crystal (LC) composite gels. The mechanical strength of the colloidal gels can be widely tuned by varying particle concentrations. With increasing particle concentration, a storage modulus of the particle/LC composite gels increased and reached over 10⁴ Pa, showing good self-supporting ability. We demonstrated for the first time that the particle/LC composite gels exhibited rapid and repetitive recovery of the mechanical strength after large-amplitude oscillatory breakdown. In addition, photoresponsive properties of the composite gels were investigated by the <i>cis</i>–<i>trans</i> photoisomerization of the azobenzene compound doped into the host LCs. The photochemical gel–sol transition could be repeatedly induced by changing the phase structure of the host LCs between nematic and isotropic, using the photoisomerization. The particle/LC composite gels can be applied to optically healable materials by the site-selective gel–sol transition based on the photochemical modulation of the phase structures of the host LCs

Convenio Marco de Cooperación entre la Universidad Nacional de La Plata y la Universidad Nacional del Litoral

Ambas Universidades se comprometen a colaborar en actividades de formación de personal docente, de investigación científica y desarrollo tecnológico, al intercambio de profesores y estudiantes y en la utilización y comercialización a terceros de tecnologías desarrolladas por ambas instituciones, mediante la suscripción de convenios específicos.Universidad Nacional de La Plat

Dual Self-Healing Abilities of Composite Gels Consisting of Polymer-Brush-Afforded Particles and an Azobenzene-Doped Liquid Crystal

We prepared the composite gels from polymer-brush-afforded silica particles (P-SiPs) and an azobenzene-doped liquid crystal, and investigated their inner structure, dynamic viscoelastic properties, thermo- and photoresponsive properties, and self-healing behaviors. It was found that the composite gels had a sponge-like inner structure formed with P-SiPs and exhibited good elastic property and shape recoverability. The surface dents made on the composite gel could be repaired spontaneously at room temperature. Moreover, the composite gel exhibited a gel–sol transition induced by the <i>trans</i>–<i>cis</i> photoisomerization of the azo dye, and the transition could be used as a mending mechanism for surface cracks. Consequently, we successfully developed a material exhibiting two types of self-healing abilities simultaneously: (1) spontaneous repair of surface dents by means of the excellent elasticity of the composite gel and (2) light-assisted mending of surface cracks by photoinduced gel–sol transition

Growth of Cuprous Oxide Particles in Liquid-Phase Synthesis Investigated by X‑ray Laser Diffraction

Cuprous oxide (Cu₂O) particles obtained by surfactant-assisted liquid-phase synthesis have cuboid shapes but the internal structures are difficult to be visualized by electron microscopy. Herein, we investigated the internal structures of numerous individual Cu₂O particles with submicrometer dimensions by X-ray diffraction imaging (XDI) using X-ray free-electron laser (XFEL) pulses. The reconstructed two-dimensional electron density maps, which displayed inhomogeneous internal structures, were divided into five classes characterized by the positions and shapes of high and low electron density areas. Further analysis of the maps in each class by a manifold learning algorithm revealed that the internal structures of Cu₂O particles varied in correlation with total electron density while retaining the characteristics within each class. On the basis of the analyses, we proposed a growth mechanism to yield the inhomogeneity in the internal structures of Cu₂O particles in surfactant-mediated liquid-phase synthesis

Design of Roughened Current Collector by Bottom-up Approach Using the Electroplating Technique: Charge–Discharge Performance of a Sn Negative-Electrode for Na-Ion Batteries

The use of high capacity electrode materials based on alloying and dealloying reactions with Na is very effective for improving energy density of batteries. However, their application brings on electrical isolation such as detachment of the electrode mixture layer from a current collector, causing rapid capacity fading. We previously found that Cu electrochemically grows in sheet form by electroplating in a CuSO₄-based aqueous solution with poly­(acrylic acid) (PAA). In the present study, our goal was to elucidate the formation mechanism of Cu sheets by characterization using scanning transmission electron microscopy (STEM), X-ray diffraction (XRD) analysis, and electron scatter diffraction patterns (EBSD) mapping. Then, the cycling performance of a Sn negative electrode for Na-ion batteries was significantly upgraded by the application of a roughened-Cu substrate with optimized sheet thickness. The STEM images and EBSD maps revealed that the Cu sheet was a single crystal, and the results obtained from XRD and the cathodic polarization behavior of Cu electrodeposition in PAA-containing solutions suggested that PAA molecules adsorbed onto Cu (100) to suppress the Cu growth on the plane, resulting in the formation of Cu sheets. Although the initial reversible capacities of flat-Cu/Sn and roughened-Cu/Sn electrodes were comparable, the developed Cu substrate (1.0 × 10^–4 M PAA) delivered a noticeable increase in the reversible capacity by 210 mA h g^–1 from the first to the second cycle, whereas the flat-Cu remained the increase by 100 mA h g^–1. In addition, the roughened-Cu substrate suppressed the detachment of the active material layer to maintain a high capacity of 685 mA h g^–1 with good capacity retention of more than 90% by the anchor effect. These results demonstrate that the roughened-Cu substrate prepared in the present work is a promising candidate as a current collector for rechargeable batteries

Water Encapsulation Control in Individual Single-Walled Carbon Nanotubes by Laser Irradiation

Owing to one-dimensionality, nanoscale curvature, and high chemical stability, single-walled carbon nanotubes (SWNTs) have unique surfaces for gas molecules: outer surface as adsorption (exohedral) site and inner surface that provides encapsulation (endohedral) space. Because as-grown SWNTs have different structure (chirality and diameter) and they are normally bundled, it is extremely difficult to investigate the intrinsic properties of SWNTs as adsorbent. Here we demonstrate controlling adsorption and encapsulation states of water in individual suspended SWNTs using laser irradiation with monitoring of their behavior by photoluminescence measurement and perform molecular dynamics simulation. The laser heating and the pressure control make water molecules encapsulated or ejected for SWNTs, which are individually oxidized and opened with laser heating. The precise control of oxidization makes it possible to observe the cluster formation of water molecules during the encapsulation process and to confine water molecules inside SWNTs even in vacuum

Three Gel States of Colloidal Composites Consisting of Polymer-Brush-Afforded Silica Particles and a Nematic Liquid Crystal with Distinct Viscoelastic and Optical Properties

Colloidal composites consisting of polymer-brush-afforded silica particles (P-SiPs) and a nematic liquid crystal (LC) exhibited three gel states with distinct viscoelastic and/or optical properties depending on temperature: (1) opaque hard gel, (2) translucent hard gel, and (3) translucent soft gel. We demonstrated that the transitions of the optical property and the hardness of the gels were due to the phase transition of the LC matrix and the glass transition of the grafted polymers of P-SiPs, respectively. We then revealed that the gelation (the formation of the translucent soft gel) was caused by the phase separation of P-SiPs and LC matrix in an isotropic phase based on spinodal decomposition. In addition, the particle concentration and molecular weight of the grafted polymer of P-SiPs were observed to significantly affect the elastic moduli and thermal stability of the composite gels. By the addition of an azobenzene derivative into an LC matrix, we achieved photochemical switching of the transparency of the composites based on the photoinduced phase transition of LCs, while keeping self-supporting ability of the composite gel

Tuning of the Thermoelectric Properties of One-Dimensional Material Networks by Electric Double Layer Techniques Using Ionic Liquids

We report across-bandgap p-type and n-type control over the Seebeck coefficients of semiconducting single-wall carbon nanotube networks through an electric double layer transistor setup using an ionic liquid as the electrolyte. All-around gating characteristics by electric double layer formation upon the surface of the nanotubes enabled the tuning of the Seebeck coefficient of the nanotube networks by the shift in gate voltage, which opened the path to Fermi-level-controlled three-dimensional thermoelectric devices composed of one-dimensional nanomaterials

TRAM Is Involved in IL-18 Signaling and Functions as a Sorting Adaptor for MyD88

<div><p>MyD88, a Toll/interleukin-1 receptor homology (TIR) domain-containing adaptor protein, mediates signals from the Toll-like receptors (TLR) or IL-1/IL-18 receptors to downstream kinases. In MyD88-dependent TLR4 signaling, the function of MyD88 is enhanced by another TIR domain-containing adaptor, Mal/TIRAP, which brings MyD88 to the plasma membrane and promotes its interaction with the cytosolic region of TLR4. Hence, Mal is recognized as the “sorting adaptor” for MyD88. In this study, a direct interaction between MyD88-TIR and another membrane-sorting adaptor, TRAM/TICAM-2, was demonstrated <em>in vitro</em>. Cell-based assays including RNA interference experiments and TRAM deficient mice revealed that the interplay between MyD88 and TRAM in cells is important in mediating IL-18 signal transduction. Live cell imaging further demonstrated the co-localized accumulation of MyD88 and TRAM in the membrane regions in HEK293 cells. These findings suggest that TRAM serves as the sorting adaptor for MyD88 in IL-18 signaling, which then facilitates the signal transduction. The binding sites for TRAM are located in the TIR domain of MyD88 and actually overlap with the binding sites for Mal. MyD88, the multifunctional signaling adaptor that works together with most of the TLR members and with the IL-1/IL-18 receptors, can interact with two distinct sorting adaptors, TRAM and Mal, in a conserved manner in a distinct context.</p> </div

The IFN-γ production from IL-18 and/or IL-12 stimulated Th1 cells from TRAM-deficient mice and MyD88 deficient mice.

<p>The IFN-γ production levels were significantly reduced in TRAM deficient mice and MyD88 deficient mice. The black bars show the production levels from IL-18 and IL-12 co-stimulated Th1 cells, grey bars show those from IL-18 solely stimulated Th1 cells, and the white bars show those from no secondary stimulated Th1 cells.</p