Extra‐Large Mechanical Anisotropy of a Hydrogel with Maximized Electrostatic Repulsion between Cofacially Aligned 2D Electrolytes

In our previous work, we have shown that “electrostatic forces”, when generated anisotropically in aqueous media by 2D electrolytes upon cofacial orientation, enable the formation of a hydrogel with an anisotropic parameter, as defined by the ratio of elastic moduli E_⊥/E_∥, of 3.0. Herein, we successfully developed the design strategy for a hydrogel with an anisotropic parameter of no less than 85. This value is not only 28 times greater than that of our previous anisotropic hydrogel but also 6 times larger than the current champion record in synthetic hydrogels (E_⊥/E_∥～15). Firstly, we simply lowered ionic contaminants in the hydrogel and were able to enhance the anisotropic parameter from 3.0 to 18. Then, we chose a supporting polymer network allowing the hydrogel to carry a higher interior permittivity. Consequently, the anisotropic parameter was further enhanced from 18 to 85. Owing to the enhanced mechanical anisotropy, our new hydrogel displayed a superb ability of seismic isolation.     

Synthesis of Anisotropic Hydrogels and Their Applications

Owing to their water‐rich structures, which are similar to those of biological tissues, hydrogels have long been regarded as promising scaffolds for artificial tissues and organs. However, in terms of the structural anisotropy, most synthetic hydrogels are substantially different from biological systems. Synthetic hydrogels are usually composed of randomly oriented three‐dimensional polymer networks whereas biological systems adopt anisotropic structures with hierarchically integrated building units. Such anisotropic structures often play essential roles in biological systems to exhibit particular functions. In this context, anisotropic hydrogels provide an entry point for exploring biomimetic applications of hydrogels. Reflecting these aspects, an increasing number of studies on anisotropic hydrogels have been reported recently. This Minireview highlights the use and perspectives of these anisotropic hydrogels, particularly focusing on their preparation, structures, and applications.     

Stability Characteristics of Dispersed Oil Droplets Prepared by the Microchannel Emulsification Method

A novel emulsification method, microchannel (MC) emulsification, was developed for making monodispersed regular-sized droplets in our laboratory. An oil-in-water dispersed system, in which phosphate buffer was used as the continuous phase, sodium dodecyl sulfate (SDS) as the surfactant, and clove oil as the dispersed phase, was prepared by this technique. The average diameter of oil droplets was about 20 μm, with a narrow size distribution. The stability characteristics of the dispersed oil droplets were investigated by an optical microscope and kinetic light scattering method. The stability of the dispersed oil droplets depended on the SDS concentration. When the SDS concentration was above the critical micelle concentration (CMC), the turbidity of the dispersed solution sharply increased at the initial stage. Optical microscopic observation has confirmed that a part of the oil droplets broke up with time, and submicrometer droplets appeared. On the other hand, when the SDS concentration was below the CMC, the turbidity of the dispersed solution had little change in the initial stage, showing that the oil droplets were very stable. The effect of ion concentration was also examined. The results showed that the stability of the oil droplets depended on the balance of the Van der Waals attraction and electrical repulsion between the oil droplets in low ion concentration. Copyright 2001 Academic Press.     

Production of aliphatic aldehydes on peroxidation of various types of lipids.

IN vitro peroxidation by air, or xanthine-xanthine oxidase (xanthine-XOD) was performed to estimate the production of aliphatic aldehydes from free polyunsaturated fatty acids (PUFA), triglycerides, phospholipids and rat liver microsomes and mitochondria. The aldehyde contents in peroxidized lipids were determined by liquid chromatography and fluorescence detection. In both peroxidation, pentanal, (E)-4-hydroxy-2-nonenal (4-HN), and hexanal were produced from omega-6 PUFA rich lipids and propanal was markedly enhanced by increasing the degree of fatty acid unsaturation. The ratios of 4-HN to hexanal production in xanthine-XOD peroxidation of the omega-6 PUFA rich lipids, and rat liver microsomes and mitochondria were much higher than those in air peroxidation. The ratios (4-HN/hexanal) obtained in microsomes and mitochondria by xanthine-XOD were similar to those in rat liver observed in vitamin E deficient studies. The determination of these aldehydes may be useful to estimate the kinds of fatty acids peroxidized and investigate in vivo lipid peroxidation mechanism.     

Extraction and spectrophotometric determination of vanadium with 4-(2-thiazolylazo)resorcinol and tetraphenylarsonium and phosphonium chlorides

Extraction of vanadium-4-(2-thiazolylazo)resorcinol complexes by quaternary salts such as triphenylmethylarsonium iodide, tetraphenylarsonium chloride, and tetraphenylphosphonium chloride has been studied. Quantitative extraction is achieved with tetraphenylarsonium and tetraphenylphosphonium chlorides in the pH region between 3.5 and 5. The optimum conditions for the extraction and spectrophotometric determination of vanadium in the extract are: pH 3.8–4.0, the concentration of vanadium 0.1–0.4 μg/ml. Effective molar absorptivity at λ_max = 555 is (2.55 ± 0.05) × 10⁴ liters mol⁻¹ cm⁻¹. Beer's law is obeyed. Relative standard deviation is 2–10% depending on the concentration level. The composition of the extracted complexes was studied in the solution and in the solid state. For their characterization chemical and spectral evidence and comparison with the vanadium-PAR complexes have been combined.     

Zone electrophoresis separation of perfluorocarboxylic acids on a chip with conductivity detection

Perfluorinated carboxylic acids (PFCAs), amphiphiles of anthropogenic origin, are spread worldwide throughout the environment. This work deals with their zone electrophoresis (ZE) separation on a chip with coupled columns and integrated conductivity detection. Analogies with the electrophoretic behavior of PFCAs and fatty acids were employed in a search for electrolyte conditions suitable for their separation. ZE separations in the water-ethanol electrolyte systems, based on differences in the ionic mobilities of the anions of PFCAs, provided favorable resolution and detection conditions of the homologues containing up to 10 carbon atoms in the alkyl chain. Concentration limits of detection of 0.3-6.5 micromol/L were attained for PFCAs (loaded by a 900 nL volume sample injection channel of the chip) under these separation conditions. The material of which the chip was made [poly(methylmethacrylate)] restricted its use in investigations of the separations of higher PFCA homologues as it was damaged by ethanolic and/or methanolic background electrolyte solutions required in experiments with these amphiphilic compounds.     

Selective vinyl cationic polymerization of monomers with two cationically polymerizable groups. IV. New initiating systems for selective and living polymerization of p-isopropenylphenyl glycidyl ether

A variety of cationic initiators were employed for p-isopropenylphenyl glycidyl ether (IPGE), an α-methylstyrene derivative with an epoxy pendant, and optimum initiators and reaction conditions were evaluated in terms of its selective vinyl polymerization and living polymerization. Despite the coexistence of two cationically polymerizable groups in IPGE, binary initiating systems (HI, CF₃COOH, or CH₃CH(OiBu)-OCOCH₃, each coupled with ZnI₂) and sulfonic acids (CF₃SO₃H and CH₃SO₃H) selectively polymerized the vinyl group of IPGE in CH₂Cl₂ at ?78°C to produce soluble polymers with epoxy pendant groups in high yield. Metal halides (BF₃OEt₂ and AlEtCl₂) polymerized both the vinyl and epoxy groups of IPGE to give crosslinked insoluble polymers. In contrast, under these conditions, the HI/ZnI₂ system also led to a long-lived polymer, the molecular weight of which increased upon addition of a fresh feed of monomer to a completely polymerized reaction mixture, whereas the use of other initiators resulted in nonliving polymers. At higher temperatures (?40 and ?15°C), soluble poly(IPGE) was also obtained with HI/ZnI₂, but the polymer yield decreased with raising temperature, because of the occurrence of termination reaction.     

Synthesis and characterization of a novel terthiophene-based quinodimethane bearing a 3,4-ethylenedioxythiophene central unit

The synthesis and a combined spectroscopic and density functional theoretical characterization of a 3',4'-ethylenedioxy-5,5' '-bis(dicyanomethylene)-5,5' '-dihydro-2,2':5',2' '-terthiophene analogue of 7,7,8,8-tetracyanoquinodimethane (TCNQ) are presented. Electrochemical data show that this novel trimer can be both reversibly reduced and oxidized at relatively low potentials. Quantum-chemical calculations show that the compound exhibits a quinoidal structure in its ground electronic state and that a certain degree of intramolecular charge transfer takes place from the central terthienyl moiety toward both =C(CN)2 end-caps. Therefore, the amphoteric redox behavior of this novel material can be related to the coexistence of an electron-impoverished terthienyl core endowed by two electron-enriched =C(CN)2 substituents. The UV-vis spectrum is dominated by the appearance of a strong absorption near 660 nm, attributable to the highest occupied molecular orbital (HOMO) --> lowest unoccupied molecular orbital (LUMO) pi-pi electronic transition of the terthienyl spine on the basis of time-dependent density functional theory (DFT) computations. The DFT calculations performed on the minimum-energy molecular geometry about the equilibrium atomic charge distribution, topologies, and energies of the frontier orbitals around the gap and about the Raman-active vibrations associated with the strongest Raman features are also consistent with a rather effective pi-electron conjugation and the partial degree of intramolecular charge transfer mentioned above. Our study reveals this novel heteroquinoid trimer could act as a promising candidate in organic field-effect transistor (OFET) applications.