Photoisomerization-induced solubility change of a photochromic diarylethene (DAE) derivative is investigated by a combination of theoretical calculations and experimental measurements. A significant solubility change is experimentally observed between two DAE photoisomers (open and closed forms) in n-octane solution. To elucidate the reason for the observed solubility change, we adopt a thermodynamic model and consider both ideal and nonideal contributions. The analysis revealed that both the crystalline stability of the isomers and their solute-solvent interactions play critical roles in determining the solubility difference. We believe that the current elucidation of thermodynamic properties will be useful to develop new functions of the DAE derivatives and future applications.

As organic-inorganic hybrids, necklace-type PDMS-POSS polymers were grafted onto silica particles and synthesized via a two-step ring-opening equilibrium polymerization of cyclic siloxane (D4) and bifunctional POSS. The polymers were then grafted on silica particles of different sizes (100-nm hollow particles; and 200- and 500-nm solid particles) to fabricate POSS-DMS-grafted silica composites. The materials were characterized using 1H-NMR and 29Si-NMR spectroscopy to confirm the polymer structures and the degree of grafting. Thermogravimetric analysis was used to evaluate the thermal stability and quantify the grafted organic content. The results demonstrated that the grafting efficiency and thermal properties were influenced by both the average siloxane chain length and the surface area of the silica particles. The ungrafted POSS-DMS polymers showed the highest thermal stability (Td,5% > 470 degrees C) at an average siloxane chain length of 3-4, indicating an optimal balance between POSS rigidity and siloxane flexibility. By contrast, the grafted silica samples exhibited a nearly constant Td,5% of approximately 460 degrees C, regardless of chain length. This indicates that grafting onto the silica surface restricts chain mobility and suppresses chain length-dependent thermal behavior.

New combinatorial analysis for solution crystal engineering on an open lab-on-a-chip by combining the inkjet method and non-volatile solvents.

Various crosslinked PDMS films incorporating cyclic epoxy groups were prepared by UV-induced acid generation and thermal curation and evaluated as CO₂-selective permeable membranes. These free-standing, ultrathin PDMS films (~100 nm thick) were formed by crosslinking side-epoxy-PDMS, which contains multiple epoxy groups, and end-epoxy-PDMS, which has epoxy groups at the polymer ends only. Gas permeation tests revealed that the films crosslinked with end-epoxy-PDMS exhibited high CO₂ permeance. Specifically, the membrane composed of UV-crosslinked end-epoxy-PDMS (Mn = 20,000, thickness ~ 200 nm) achieved a CO₂ permeance of 5200 GPU and a CO₂/N₂ selectivity of 11.0. Reducing the membrane thickness increased the permeance without affecting selectivity. However, shortening the siloxane chain, using side-epoxy-PDMS, or reducing the linker length led to decreases in both permeance and selectivity. For example, side-epoxy-PDMS (Mn = 30,000, Si-H/O-Si-O ratio = 37%, thickness ~ 200 nm) had a CO₂ permeance of 400 GPU and a CO₂/N₂ selectivity of 1.16. These results indicate that a lower crosslinking density and longer end-epoxy-PDMS siloxane chains are advantageous for CO₂ dissolution and diffusion, resulting in superior CO₂ permeance and selectivity compared with composed of side-epoxy-PDMS.

Crystal engineering for single crystallization of pi-conjugated molecules has attracted much attention because of their electronic, photonic, and mechanical properties. However, reproducibility is a problem in conventional printing techniques because control of solvent evaporation is difficult. We investigated the phase diagrams of two anthracene derivatives in synthesized ionic liquids for non-volatile crystal engineering to determine the critical points for nucleation and crystal growth. Anthracene and 9,10-dibromoanthracene were used as representative pi-conjugated molecules that form crystal structures with different packing types. Ionic liquids with an alkylpyridinium cation and bis(fluorosulfonyl)amide were good solvents for the anthracene derivatives from ca. 0 degrees C to 200 degrees C. The solubilities (critical points for crystal growth) of the anthracene derivatives in the ionic liquids reached the 100mM level, which is similar to those in organic solvents. Ionic liquids with phenyl and octyl groups tended to show high-temperature dependence (a high dissolution entropy) with 9,10-dibromoanthracene. The precipitation temperature (critical point for crystal nucleation) at each 9,10-dibromoanthracene concentration was lower than the dissolution temperature. The differences between the dissolution and precipitation temperatures (supersaturated region) in the ionic liquids were greater than those in an organic solvent.

The problem of plastic waste in the environment calls for the development of new polymeric materials designed specifically for easy recycling at the end of their life cycle. Herein, a green polymer system comprising a series of necklace-shaped polydimethylsiloxanes bearing anthracene dimer units is developed. The polymers have low environmental impact and are easily recycled. Further, their flexibility and glass transition temperatures are easy to control. These necklace-shaped inorganic polymers are synthesized by photopolymerizing (dimerizing) anthracene-terminated oligo-dimethylsiloxane monomers. A key achievement of the present work is the successful chemical recovery of the monomers from the polymers through thermal depolymerization, enabling monomer-polymer recycling. By applying equilibrium polymerization with base catalysts, monomers with a controlled distributed chain length are synthesized from monomers with a constant chain length. The necklace-shaped polymers synthesized from these randomized monomers have amorphous structures and readily form transparent films. It is possible to modulate the thermal and mechanical properties of the polymers by controlling the average chain length of the polydimethylsiloxane between the anthracene dimers. This investigation presents a method for the synthesis and cyclic utilization of polymer materials with a wide range of applications, including plastics and elastomers.

In this study, we present an innovative approach for creating hierarchical meso/nanoporous Pt films using dynamic soft templating. The fabrication process, called dynamic soft templating, involves Pt electrodeposition within a specialized bicontinuous microemulsion (BME) system characterized by a sophisticated three-dimensional network comprising water and oil phases, surfactants, and cosurfactants. Pt electrodeposition exclusively occurs in the water phase of the BME. This results in a porous Pt film exhibiting a nanostructure mirroring the oil solution/water solution nanostructure (solution/solution structure) of the BME, the size of which can be tailored by adjusting the BME composition. Through a simultaneous interplay of Pt electrodeposition and overpotential deposition of hydrogen (H-OPD, dissociative adsorption of water), potential-dependent Pt mesostructures are dynamically shaped. As a result, we achieve diverse morphologies in the form of hierarchical meso/nanoporous Pt films. The potential applications of the films are evaluated as electrocatalysts for the methanol oxidation reaction (MOR), and it was found that the electrocatalytic performances seem to be sensitive to nanoporosity and not relevant to mesoporosity.

Fabrication and observation of highly ordered molecular adlayers by electrochemical scanning tunneling microscopy operating at solid–liquid interfaces under electrochemical conditions are discussed. Electrochemical scanning tunneling microscopy enables near real-time and real-space observation of inner molecular structures, molecular self-assembly, and dynamics, including the "order–disorder" and "order–order" phase transitions. By finely controlling the electrochemical potential, it is possible to precisely control the adsorption strength and surface concentration of molecules at the solid–liquid interface, allowing visualization of the behavior and dynamic changes of molecules as a function of the potential.

We demonstrate the fabrication of millimeter-sized single crystals of 0D-Cs4PbBr6 grown in a supersaturated solution consisting of organic solvents without HBr (aq). One of the precursors, CsBr, was dissolved in ethylene glycol (EG) mixed with dimethyl sulfoxide, which is a good solvent for the other precursor, PbBr2. At a solvent ratio of 20 vol % EG, the solubility of cesium bromide decreased and the title compound, Cs4PbBr6, was selectively formed, whereas, with an EG ratio of 80 vol %, 3D-CsPbBr3 was formed. A phase diagram (solubility curve) of Cs4PbBr6 in the mixed solvent containing 20 vol % EG was obtained by visually observing dissolution and crystal precipitation while changing the temperature. Because the solubility was proportional to the temperature, the solubility curve demonstrated an upper critical solution phenomenon. The solubility near the boiling point of the solution (150 °C) was approximately 0.14 M. A single crystal of Cs4PbBr6 was formed by growing a seed crystal in a supersaturated solution on the low-temperature side of the solubility curve. X-ray analysis established the crystal structure; a fluorescence emission at 520 nm with a full width at half maximum of 20 nm confirms the composition of the single crystal to be Cs4PbBr6.

Polyaniline-based atomic switches are material building blocks whose nanoscale structure and resultant neuromorphic character provide a new physical substrate for the development next-generation, nanoarchitectonic-enabled computing systems. Metal ion-doped devices consisting of a Ag/metal ion doped polyaniline/Pt sandwich structure were fabricated using an in situ wet process. The devices exhibited repeatable resistive switching between high (ON) and low (OFF) conductance states in both Ag+ and Cu2+ ion-doped devices. The threshold voltage for switching was>0.8 V and average ON/OFF conductance ratios (30 cycles for 3 samples) were 13 and 16 for Ag+ and Cu2+ devices, respectively. The ON state duration was determined by the decay to an OFF state after pulsed voltages of differing amplitude and frequency. The switching behaviour is analagous to short-term (STM) and long-term (LTM) memories of biological synapses. Memristive behaviour and evidence of quantized conductance were also observed and interpreted in terms of metal filament formation bridging the metal doped polymer layer. The successful realization of these properties within physical material systems indicate polyaniline frameworks as suitable neuromorphic substrates for in materia computing.

HYPOTHESES:Bicontinuous microemulsions (BMEs) have attracted attention as unique heterogeneous mixture for electrochemistry. An interface between two immiscible electrolyte solutions (ITIES) is an electrochemical system that straddles the interface between a saline and an organic solvent with a lipophilic electrolyte. Although most BMEs have been reported with nonpolar oils, such as toluene and fatty acids, it should be possible to construct a sponge-like three-dimensionally expanded ITIES comprising a BME phase. EXPERIMENTS:Dichloromethane (DCM)-water microemulsions stabilized by a surfactant were investigated in terms of the concentrations of co-surfactants and hydrophilic/lipophilic salts. A Winsor III microemulsion three-layer system, consisting of an upper saline phase, a middle BME phase, and a lower DCM phase, was prepared, and electrochemistry was conducted in each phase. FINDINGS:We found the conditions for ITIES-BME phases. Regardless of where the three electrodes were placed in the macroscopically heterogeneous three-layer system, electrochemistry was possible, as in a homogeneous electrolyte solution. This indicates that the anodic and cathodic reactions can be divided into two immiscible solution phases. A redox flow battery comprising a three-layer system with a BME as the middle phase was demonstrated, paving the way for applications such as electrolysis synthesis and secondary batteries.

Two-dimensional (2D) metallic nanomaterials have received much attention as next-generation materials. The creation of the characteristic pores into 2D metallic materials is expected to improve performance in sensing, surface-enhanced Raman spectroscopy, electrocatalytic activity, and so on. Here, we report that gold electrodeposition in a toluene-based bicontinuous microemulsion (BME), called a dynamic soft template, provides porous gold nanomesh (PGNM) film. The selective toluene adsorption onto Au{111} surfaces induces anisotropic 2D growth of gold in the aqueous phase of BME, and an intertwined network of water and toluene nanochannels in BME resulted in the formation of abundant in-plane nanopores. Toluene adsorption during Au electrodeposition makes the {111}-oriented Au surfaces more lipophilic, i.e., a structural change in BME is induced to expose the organic phase solution selectively to the toluene-adsorbed {111} Au surfaces. This dynamic change in the BME solution structure during electrodeposition might enhance the anisotropic growth of gold (dynamic soft templating). Electrochemical behaviors of low-index planes of Au electrode supported the growth mechanism of PGNM film.

K4Nb6O17·3H2O-based Janus nanosheets with water dispersibility and surface activity were prepared via sequential regioselective surface modification. To provide individual Janus nanosheets with these two properties, phenylphosphonic acid and phosphoric acid were utilized for surface modification at interlayers I and II of K4Nb6O17·3H2O, respectively, and the resulting product was exfoliated into single-layered nanosheets by ultrasonication in water. The resulting aqueous dispersion of the Janus nanosheets showed lower surface tension than pure water, confirming that the Janus nanosheets had surface activity. An o/w emulsion was formed using the Janus nanosheet aqueous dispersion and toluene. In this emulsion, characteristic phenomena, coalescence and Ostwald ripening behaviour of toluene droplets were observed; the appearance of ellipsoidal droplets during coalescence and a rapid Ostwald ripening which differ from those observed for systems using conventional surfactants, were observed. These phenomena likely originated from the unique anisotropic structures of Janus nanosheets with their nm-scale thickness and μm-range lateral size.

We evaluated the dispersion and diffusion of fluorescent-labeled lipophilic vitamin E (VE) in microemulsions (MEs) including water-in-oil (W/O) type ME, oil-in-water (O/W) type ME, and bicontinuous ME (BME), using fluorescence correlation spectroscopy (FCS). We prepared a fluorescent ATTO 488 or BODIPY group labeled VE (VE-ATTO or VE-BODIPY). VE-ATTO possesses lipophilic and hydrophilic parts, while VE-BODIPY consists solely of the lipophilic part. The VE-ATTO dissolved in heptane solution as an oil phase appeared hot pink in color due to the solvatochromism effect under room light and almost no fluorescent signal, which was unlike the VE-ATTO dissolved in ME solutions and all the VE-BODIPY solutions (typical fluorescent green color). The FCS measurement proved that VE-BODIPY diffuses faster than VE-ATTO. This is presumably because the "surfactant-like" VE-ATTO is localized and trapped at the micro-water/micro-oil interface of the MEs, while the VE-BODIPY exists in the ME phase and macro-oil phase with good dispersion. These results demonstrate that FCS is a powerful tool for the rapid evaluation of the lipophilic probe behavior in heterogeneous ME solutions.

Invited for the cover of this issue is the group of Biplab Manna at the University of Kumamoto. The image depicts various kinds of stacking between the metal-organic layers of MOFs. Read the full text of the article at 10.1002/chem.202201665.

Double-layered nanosheets containing pH-cleavable polymer networks between two niobate layers were prepared by copolymerization of N-isopropylacrylamide and an acid-degradable crosslinker via surface-initiated atom transfer radical polymerization on the surface of hydrated interlayers (interlayer I) of K4Nb6O17·3H2O and subsequent exfoliation by the introduction of tetra-n-butylammonium (TBA) ions into anhydrous interlayers (interlayer II). Moreover, the double-layered nanosheets were converted into single-layered nanosheets by the cleavage of cross-linking points in polymer networks by lowering pH. Fourier transform infrared spectroscopy (FTIR) and thermogravimetry (TG) results showed that polymer networks were present, and nanosheets with a thickness of 10.8 ± 1.6 nm were observed by using an atomic force microscope (AFM) after exfoliation using TBA ions. The thickness of the nanosheets was decreased to 6.1 ± 0.9 nm by lowering the pH, and proton nuclear magnetic resonance (1H NMR) and UV-vis spectroscopy showed that the degradation of the cross-linkers proceeded, suggesting that the cleavage of the cross-linking points led to the conversion of double-layered nanosheets into single-layered nanosheets.

Multimode motion of Marangoni propulsion ships on a water surface as per a near-infrared, two-wavelength selective response is achieved for the first time. The ships are rhombus- or propeller-shaped polyacrylamide or siloxane resin-based gels in which Nd2O3 and Yb2O3 nanoparticles are incorporated separately for photothermal conversion at 808 and 980 nm, respectively. The rhombus geometry is for straight locomotion, and the propeller geometry is for rotation. On/off remote control of the forward and backward locomotion of a rhombus-shaped ship and of the clockwise and counterclockwise rotations of a propeller-shaped ship via irradiation with 808 or 980 nm near-infrared light is demonstrated. The nanoparticles are incorporated into the desired locations of the gels, enabling selective local heating of the gels without focusing the light. The temperature gradient of the ships by local heating, based on a photothermal conversion, generates a Marangoni propulsion force to move the ship in the desired direction.