Reconstruction of Chitosan Network Orders Using the Meniscus Splitting Method for Designing pH-Responsive Materials.

Chitosan is a product of deacetylated chitin and a natural polymer that is attractive as a functional and biocompatible material in the pursuit of alternative materials to synthetic plastics for a sustainable society. Although hierarchical architectures, from precise molecular structures to nanofibers and twisted structures, have been clarified, the expansion of the anisotropic microstructures of chitosan into millimeter-scale materials is in the process of development. In this study, a chitosan network was reconstructed from an aqueous solution by using the meniscus splitting method to form a three-dimensionally ordered microstructure. A chitosan membrane deposited on the millimeter scale formed a useful anisotropically pH-responsive hydrogel. During the evaporation of the aqueous solution from a finite space, chitosan underwent ordered deposition by capillary force to form a membrane with oriented microstructures and microlayers. Unlike the cast films formed between solid-liquid and air-liquid interfaces, this membrane formed between two air-liquid interfaces. As a result, the membranes with ordered microstructures were capable of signifying directional swelling in aqueous environments and reversible/irreversible swelling-deswelling changes by controlling the pH range. We envision that the anisotropic pH response of the chitosan network can be utilized under physiological conditions as a next-generation material.

Assembly Structure Formation in Bulk and Ultrathin Films of Poly(substituted methylene) Having an Azobenzene Side Chain.

The density of the side chain introduced to a polymer main chain greatly influences the properties and functions of the polymer. This work first reports on the packing structure and properties at an interface of a poly(substituted methylene) where an azobenzene side chain is introduced at every carbon atom in the main chain (C1PAz). The structure and properties are compared with those of a conventional vinyl polymer [poly(methacrylate)] possessing an identical side-chain structure (C2PAz). The packing structure in the bulk state analyzed by X-ray measurements revealed that C1PAz adopts a highly ordered rectangular unit cell structure, whereas C2PAz shows a less ordered lamellar one. Langmuir film balance experiments indicated that both polymers with the trans-azobenzene give essentially the identical 2D side-chain occupying area on water, which agrees well with the smectic B (hexatic packing) model based on the X-ray data. Upon transfer onto a solid substrate, only C1PAz shows a conformational transformation to a spread bilayer-type layer, most probably due to conformational frustration stemming from the crowding of the side chains. This study proposes new insights into the effects of side-chain density on the self-assembly and photoreaction of azobenzene-containing polymers, which are expected to expand the possibilities of polymer design for various applications.

Influence of Humidity on Layer-by-Layer Growth and Structure in Coordination Networks.

Metal-organic frameworks (MOFs) are promising materials because of their high designability of pores and functionalities. Especially, MOF thin films and their properties have been investigated toward applications in nanodevices. Typically, MOF thin films are fabricated by using a bottom-up method such as layer-by-layer (LbL) growth in air. Because the water molecules can coordinate and be replaced with organic linkers during synthesis, humidity conditions will be expected to influence the LbL growth processes. In this study, we fabricated MOF thin films composed of Zn2+, tetrakis-(4-carboxyphenyl)-porphyrin (TCPP), and 4,4'-bipyridyl (bpy) at 10 and 40% relative humidity (RH) conditions. Then, we investigated the humidity effects on chemical compositions of TCPP and bpy, periodic structure, orientation, and surface morphology. At high RH, coordination replacement of water with the organic linkers becomes more competitive than that at low RH, resulting in a different TCPP/bpy composition ratio between the two RH conditions. Also, more frequent coordination replacements of water with the organic linkers at high RH led to the formation of phases other than that observed at low RH, loss of growth orientation, and rough surface. The findings clarified the importance of controlling the RH condition during LbL growth to obtain the desired coordination networks.

Microfluidic Device for Simple Diagnosis of Plant Growth Condition by Detecting miRNAs from Filtered Plant Extracts.

Plants are exposed to a variety of environmental stress, and starvation of inorganic phosphorus can be a major constraint in crop production. In plants, in response to phosphate deficiency in soil, miR399, a type of microRNA (miRNA), is up-regulated. By detecting miR399, the early diagnosis of phosphorus deficiency stress in plants can be accomplished. However, general miRNA detection methods require complicated experimental manipulations. Therefore, simple and rapid miRNA detection methods are required for early plant nutritional diagnosis. For the simple detection of miR399, microfluidic technology is suitable for point-of-care applications because of its ability to detect target molecules in small amounts in a short time and with simple manipulation. In this study, we developed a microfluidic device to detect miRNAs from filtered plant extracts for the easy diagnosis of plant growth conditions. To fabricate the microfluidic device, verification of the amine-terminated glass as the basis of the device and the DNA probe immobilization method on the glass was conducted. In this device, the target miRNAs were detected by fluorescence of sandwich hybridization in a microfluidic channel. For plant stress diagnostics using a microfluidic device, we developed a protocol for miRNA detection by validating the sample preparation buffer, filtering, and signal amplification. Using this system, endogenous sly-miR399 in tomatoes, which is expressed in response to phosphorus deficiency, was detected before the appearance of stress symptoms. This early diagnosis system of plant growth conditions has a potential to improve food production and sustainability through cultivation management.

Synthesis of thermo-responsive polymer gels composed of star-shaped block copolymers by copper-catalyzed living radical polymerization and click reaction.

In recent times, there has been a significant surge in research interest surrounding thermo-responsive water-soluble polyacrylamides, primarily due to their intriguing capability to undergo significant solubility changes in water. These polymers exhibit the remarkable ability to shift from a soluble to an insoluble state in response to temperature variations. The capacity of these polymers to dynamically respond to temperature changes opens up exciting avenues for designing smart materials with tunable properties, amplifying their utility across a spectrum of scientific and technological applications. Researchers have been particularly captivated by the potential applications of thermo-responsive water-soluble polyacrylamides in diverse fields such as drug delivery, gene carriers, tissue engineering, sensors, catalysis, and chromatography separation. This study reports the construction and functionalization of polymer gels consisting of a polymer network of polyacrylamide derivatives with nano-sized structural units. Specifically, thermo-responsive polymer gels were synthesized by combining well-defined star-shaped polymers composed of polyacrylamide derivatives with a multifunctional initiator and linking method through a self-accelerating click reaction. The polymerization system employed a highly living approach, resulting in polymer chains characterized by narrow molecular weight distributions. The method's high functionality facilitated the synthesis of a temperature-responsive block copolymer gel composed of N-isopropyl acrylamide (NIPA) and N-ethyl acrylamide (NEAA). The resulting polymer gel, comprising star-shaped block copolymers of NIPA and NEAA, showcases smooth volume changes with temperature jumps.

This approach's versatility was showcased by creating networks using widely-used vinyl polymers. It can generate various functional and nearly ideal gels and elastomers, allowing for investigating fundamental aspects of polymer networks.

Optically Transparent and Color-Stable Elastomer with Structural Coloration under Elongation.

Optically transparent and colored elastomers with high toughness are expected to play an important role in the construction of advanced medical materials, wearable displays, and soft robots. In this study, we found that composite elastomers consisting of amorphous SiO2 particles homogeneously dispersed in high concentrations within a biocompatible acrylic polymer network exhibit optical transparency and bright structural colors. In the composite elastomers, the system in which the SiO2 particles form a colloidal amorphous array hardly changes its structural color hue despite deformation due to elongation. Furthermore, the composite elastomer of the SiO2 particles with the acrylic polymer network also results in high mechanical toughness. In summary, we have shown that the elastomer that exhibits fade-resistant structural coloration formed from safe materials can combine stable coloration and mechanical strength independent of their shape. This is expected to have new potential in future technologies to support our daily life.

Effect of the Poly(ethylene glycol) Diacrylate (PEGDA) Molecular Weight on Ionic Conductivities in Solvent-Free Photo-Cross-Linked Solid Polymer Electrolytes.

To obtain safe, high-performance Li-ion batteries, the development of electrolytes with high impact resistance and high ionic conductivity is important. Ionic conductivity at room temperature has been improved by using poly(ethylene glycol) (PEG) diacrylate (PEGDA) to form three-dimensional (3D) networks and solvated ionic liquids. However, the effects of the molecular weight of PEGDA on ionic conductivities and the relationship between ionic conductivities and network structures of cross-linked polymer electrolytes have not been discussed in detail. In this study, the dependence of the ionic conductivity of photo-cross-linked PEG solid electrolytes on the molecular weight of the PEGDA was evaluated. X-ray scattering (XRS) gave detailed information about the dimensions of 3D networks formed by the photo-cross-linking of PEGDA, and the effects of the network structures on the ionic conductivities were discussed.

Lyotropic Liquid Crystalline Property and Organized Structure in High Proton-Conductive Sulfonated Semialicyclic Oligoimide Thin Films.

Fully aromatic sulfonated polyimides with a rigid backbone can form lamellar structures under humidified conditions, thereby facilitating the transmission of protons in ionomers. Herein, we synthesized a new sulfonated semialicyclic oligoimide composed of 1,2,3,4-cyclopentanetetracarboxylic dianhydride (CPDA) and 3,3'-bis-(sulfopropoxy)-4,4'-diaminobiphenyl to investigate the influence of molecular organized structure and proton conductivity with lower molecular weight. The weight-average molecular weight (M w) determined by gel permeation chromatography was 9300. Humidity-controlled grazing incidence X-ray scattering revealed that one scattering was observed in the out-of-plane direction and showed that the scattering position shifted to a lower angle as the humidity increased. A loosely packed lamellar structure was formed by lyotropic liquid crystalline properties. Although the ch-pack aggregation of the present oligomer was reduced by substitution to the semialicyclic CPDA from the aromatic backbone, the formation of a distinct organized structure in the oligomeric form was observed because of the linear conformational backbone. This report is the first-time observation of the lamellar structure in such a low-molecular-weight oligoimide thin film. The thin film exhibited a high conductivity of 0.2 (±0.01) S cm-1 under 298 K and 95% relative humidity, which is the highest value compared to the other reported sulfonated polyimide thin films with comparable molecular weight.

Donor-π-Acceptor-Type Fluorinated Tolane Containing a Semifluoroalkoxy Chain as a Condensed-Phase Luminophore.

Photoluminescent liquid-crystalline (PLLC) molecules, which can easily tune the PL behavior through the crystal (Cry)-LC phase transition, have attracted significant attention. Previously, we have demonstrated that the incorporation of a semifluoroalkoxy chain into π-conjugated mesogen is a promising approach for developing PLLC molecules with PL and SmA LC characteristics. We focused on the LC and PL characteristics of the molecules induced by the semifluoroalkoxy chain and fluorinated tolanes in the condensed phase. In this study, we developed cyano- or ethoxycarbonyl-terminated donor-π-acceptor-type fluorinated tolanes containing a semifluoroalkoxy flexible chain. The cyano-terminated fluorinated tolanes exhibited intense light-blue photoluminescence in the crystalline phase and did not exhibit any LC phase. In contrast, blue photoluminescence in the ethoxycarbonyl-terminated analogs was slightly weak; however, they exhibited Cry-SmA phase transition during the heating and cooling processes. The PL intensity of the ethoxycarbonyl-terminated fluorinated tolanes significantly decreased in the SmA phase; however, their PL colors changed during the Cry-SmA phase transition. This indicates that the developed tolanes are promising temperature-dependent PL materials, such as PL thermosensors or PL thermometers.

Induction of Highly Ordered Liquid Crystalline Phase of an Azobenzene Side Chain Polymer by Contact with 4'-Pentyl-4-cyanobiphenyl: An In Situ Study.

The orientation of liquid crystal (LC) molecules is significantly governed by solid interfaces and free surfaces, and a variety of functional materials have been developed using these properties. Although LC materials are already in industrial use, particularly for LC display panels, various studies have been conducted in recent years to better grasp the interface behavior of LC molecules. In this work, we succeeded in in situ observations of induction of higher ordered LC phases at the interface between a side-chain LC azobenzene polymer film with a thickness of ∼400 nm and a low-molecular-mass nematic LC, 4'-pentyl-4-cyanobiphenyl of 35 µm thickness, using small-angle X-ray scattering measurements and polarized optical microscopy. It is revealed that the two different mesogens cooperatively form hybrid higher ordered smectic LC phases probably through weak electron transfer immediately after interfacial contact. The induction process consists of three stages in terms of dynamic structure evolutions. Upon UV irradiation, the hybrid smectic LC structure diminished. This study provides new insights into the behavior of LC molecules near the alignment film on the solid substrate.

Induced Smectic E Phase in a Binary Blend of Side-Chain Liquid Crystalline Polymers.

Two liquid crystalline polymers containing an azobenzene or cyanobiphenyl mesogenic side chain that adopt smectic A phases are mechanically mixed at 1:1 mesogen molar ratio at an isotropic phase temperature and then cooled. The resultant binary polymer mixture behaves like a single component as revealed by polarized microscopy observation and differential scanning calorimetry, indicating that the binary mixture forms a fully compatible polymer blend. Moreover, the simple polymer blend unexpectedly leads to a higher-ordered smectic E phase where a herringbone structure is formed with restricted mesogen axis rotation. These results suggest a specific intermolecular interaction between the two mesogens, thereby inducing unusual compatibilized polymer blends and the most ordered liquid crystal (LC) phase.

Shrinking rates of polymer gels composed of star-shaped polymers of N-isopropylacrylamide and dimethylacrylamide copolymers: the effect of dimethylacrylamide on the crosslinking network.

Thermoresponsive polymer gels can be applied as culture beds for cell sheets, drug release agents for drug delivery, and sensing materials. In general, the shrinkage behavior of thermoresponsive polymer gels is complex, and they may require much longer times than swelling to reach thermodynamically stable shrinkage states. This slow volume change during shrinkage is often a drawback in using reversible changes in polymer gel volumes with changing temperature for applications such as those described above, and attempts have been made to improve the shrinkage rates of polymer gels. However, using the conventional method results in a low density of the three-dimensional crosslinked network comprising the polymer gel, which weakens the mechanical properties of the polymer gel. In this study, we investigated the effects of monomer arrangement and composition for star-shaped polymers composed of N-isopropylacrylamide and N,N-dimethylacrylamide on the shrinkage behavior of gels comprising star-shaped polymers with the aim of increasing their shrinkage rates without reducing the network densities of the temperature-responsive polymer gels. Based on selective network decomposition by methanolysis and SAXS measurements, the network structures of the obtained spherical gels were found to be more homogeneous than those of polymer gels obtained by conventional free radical polymerization. These gels exhibited reversible volume changes in water, with low-temperature swelling and high-temperature shrinkage. The rates of volume changes from a high temperature shrunken state to a low temperature swollen one were almost the same for all gels. However, the rates of volume changes from low-temperature swollen states to high-temperature shrunken states varied greatly depending on the compositions and sequences of monomers that made up the polymer networks. We confirmed that the introduction of more than 20% DMA as a block copolymer in the network suppressed phase separation and formation of a skin layer and the water inside the polymer gel drained smoothly to the outside, which resulted in an increase in the shrinkage speed.

Solvent- and Light-Sensitive AIEE-Active Azo Dye: From Spherical to 1D and 2D Assemblies.

Fluorescent molecular assembly systems provide an exciting platform for creating stimuli-responsive nano- and microstructured materials with optical, electronic, and sensing functions. To understand the relationship between (i) the plausible molecular structures preferentially adopted depending on the solvent polarity (such as N,N-dimethylformamide [DMF], tetrahydrofuran [THF], and toluene), (ii) the resulting spectroscopic features, and (iii) self-assembled nano-, micro-, and macrostructures, we chose a sterically crowded triangular azo dye (3Bu) composed of a polar molecular core and three peripheral biphenyl wings. The chromophore changed the solution color from yellow to pink-red depending on the solvent polarity. In a yellow DMF solution, a considerable amount of the twisted azo form could be kept stable with the help of favorable intermolecular interactions with the solvent molecules. By varying the concentration of the DMF solution, the morphology of self-assembled structures was transformed from nanoparticles to micrometer-sized one-dimensional (1D) structures such as sticks and fibers. In a pink-red toluene solution, the periphery of the central ring became more planar. The resulting significant amount of the keto-hydrazone tautomer grew into micro- and millimeter-sized 1D structures. Interestingly, when THF-H2O (1:1) mixtures were stored at a low temperature, elongated fibers were stacked sideways and eventually developed into anisotropic two-dimensional (2D) sheets. Notably, subsequent exposure of visible-light-irradiated sphere samples to solvent vapor resulted in reversible fluorescence off↔on switching accompanied by morphological restoration. These findings suggest that rational selection of organic dyes, solvents, and light is important for developing reusable fluorescent materials.

Simple linear ionic polysiloxane showing unexpected nanostructure and mechanical properties.

Polysiloxanes are ubiquitous materials in industry and daily life derived from silicates, an abundant resource. They exhibit various properties, which depend on the main-chain network structure. Linear (1D backbone) polysiloxanes provide amorphous materials. They are recognized as fluid materials in the form of grease or oil with a low glass transition temperature. Herein we report that a simple linear polysiloxane, poly(3-aminopropylmethylsiloxane) hydrochloride, shows an elastic modulus comparable to that of stiff resins such as poly(tetrafluoroethylene). By introducing an ammonium salt at all the units of this polysiloxane, inter- and intramolecular ionic aggregates form, immensely enhancing the elastic modulus. This polysiloxane is highly hygroscopic, and its modulus can be altered reversibly 100 million times between moist and dry atmospheres. In addition, it works as a good adhesive for glass substrates with a shear strength of more than 1 MPa in the dry state. Despite its simple structure with a flexible backbone, this polymer unexpectedly self-assembles to form an ordered lamellar nanostructure in dry conditions. Consequently, this work reveals new functions and possibilities for polysiloxanes materials by densely introducing ionic groups.

Photoisomerization-induced patterning of ion-pairing materials based on anionic azobenzene and its complex with a fluorescent π-electronic system.

Large mass transport driven by the difference in the photoisomerization-induced surface tension was demonstrated in ion pairs of anionic azobenzene and a cationic polymer. This material motion enabled fluorescence patterning using a trace amount of photoisomerized azobenzenes in complex form with a π-electronic system.

The Detection of Hyaline Casts in Patients Without Renal Dysfunction Suggests Increased Plasma BNP.

BACKGROUND AND AIM: Casts in urinary sediments are useful in the identification of kidney diseases. Among them, hyaline casts have not previously been considered as pathognomonic. However, hyaline casts can occasionally be found in patients undergoing cardiovascular treatment without renal dysfunction. We evaluated the background of these patients and also investigated their levels of plasma brain natriuretic peptide (BNP). MATERIALS AND METHODS: Samples from patients who visited the Division of Cardiovascular Disease at Nihon University Hospital (2014-2018) were examined. We set extract conditions from the laboratory information system database, setting the threshold over 60 mL/min/1.73 m2 for the estimated glomerular filtration rate (eGFR), and proteinuria as absent (-) or trace (±). One hundred forty-seven of 3137 (4.7%) samples showed hyaline casts (M:F=102:45, mean age 69.5±11.2 years). Samples with hyaline casts were divided into three rank groups. We compared BNP levels among each cast group and age-matched controls using Kruskal-Wallis analysis. RESULTS: The median BNP levels of the controls and the three casts groups were 23.3 pg/mL in the controls, 31.1 pg/mL in group (1+), 35.5 pg/mL in group (2+), and 45.8 pg/mL in group (≥3+). The median BNP levels differed significantly between two casts groups (group (2+) and group (≥3+)) and the control group (P<0.05 and P<0.01, respectively). CONCLUSION: Hyaline casts could be detected in patients with normal renal function. When hyaline casts are more than 2+, the physician should consider checking plasma BNP levels of the patient.

Incorporation of tetracarboxylate ions into octacalcium phosphate for the development of next-generation biofriendly materials.

Octacalcium phosphate (OCP; Ca8(HPO4)2(PO4)4 ∙ 5H2O) is a precursor of hydroxyapatite found in human bones and teeth, and is among the inorganic substances critical for hard tissue formation and regeneration in the human body. OCP has a layered structure and can incorporate carboxylate ions into its interlayers. However, studies involving the incorporation of tetracarboxylic and multivalent (pentavalent and above) carboxylic acids into OCP have not yet been reported. In this study, we investigate the incorporation of pyromellitic acid (1,2,4,5-benzenetetracarboxylic acid), a type of tetracarboxylic acid, into OCP. We established that pyromellitate ions could be incorporated into OCP by a wet chemical method using an acetate buffer solution containing pyromellitic acid. The derived OCP showed a brilliant blue emission under UV light owing to the incorporated pyromellitate ions. Incorporation of a carboxylic acid into OCP imparted new functions, which could enable the development of novel functional materials for biomedical applications.

Visualizing the helical stacking of octahedral metallomesogens with a chiral core.

A combination of grazing-incidence X-ray diffraction and molecular dynamics simulation studies led to the visualization of the stacking structure of a helical columnar liquid crystal formed by enantiopure octahedral metallomesogens with ΔΛ chirality. The helical structure was elucidated as a hybrid of two major proposed structures.

Hexagonal ordering of racemic Ni(II) complexes in the interlayer space of a clay mineral.

The molecular arrangement of racemic [Ni(phen)3]2+ complexes in the interlayer space of montmorillonite was investigated using X-ray diffraction measurements. When the amount of the adsorbed complexes exceeded the cation exchange capacity, they were found to form a double-molecular layer with the 2D hexagonal arrangement in the interlayer space.

Photo-triggered large mass transport driven only by a photoresponsive surface skin layer.

Since the discovery 25 years ago, many investigations have reported light-induced macroscopic mass migration of azobenzene-containing polymer films. Various mechanisms have been proposed to account for these motions. This study explores light-inert side chain liquid crystalline polymer (SCLCP) films with a photoresponsive polymer only at the free surface and reports the key effects of the topmost surface to generate surface relief gratings (SRGs) for SCLCP films. The top-coating with an azobenzene-containing SCLCP is achieved by the Langmuir-Schaefer (LS) method or surface segregation. A negligible amount of the photoresponsive skin layer can induce large SRGs upon patterned UV light irradiation. Conversely, the motion of the SRG-forming azobenzene SCLCP is impeded by the existence of a LS monolayer of the octadecyl side chain polymer on the top. These results are well understood by considering the Marangoni flow driven by the surface tension instability. This approach should pave the way toward in-situ inscription of the surface topography for light-inert materials and eliminate the strong light absorption of azobenzene, which is a drawback in optical device applications.