Spinodal decomposition of chemically fueled polymer solutions.

Ligands that accelerate nanoceria dissolution may greatly affect its fate and effects. This project assessed the carboxylic acid contribution to nanoceria dissolution in aqueous, acidic environments. Nanoceria has commercial and potential therapeutic and energy storage applications. It biotransforms in vivo. Citric acid stabilizes nanoceria during synthesis and in aqueous dispersions. In this study, citrate-stabilized nanoceria dispersions (∼4 nm average primary particle size) were loaded into dialysis cassettes whose membranes passed cerium salts but not nanoceria particles. The cassettes were immersed in iso-osmotic baths containing carboxylic acids at pH 4.5 and 37 °C, or other select agents. Cerium atom material balances were conducted for the cassette and bath by sampling of each chamber and cerium quantitation by ICP-MS. Samples were collected from the cassette for high-resolution transmission electron microscopy observation of nanoceria size. In carboxylic acid solutions, nanoceria dissolution increased bath cerium concentration to >96% of the cerium introduced as nanoceria into the cassette and decreased nanoceria primary particle size in the cassette. In solutions of citric, malic, and lactic acids and the ammonium ion ∼15 nm, ceria agglomerates persisted. In solutions of other carboxylic acids, some select nanoceria agglomerates grew to ∼1 micron. In carboxylic acid solutions, dissolution half-lives were 800–4000 h; in water and horseradish peroxidase they were ≥55,000 h. Extending these findings to in vivo and environmental systems, one expects acidic environments containing carboxylic acids to degrade nanoceria by dissolution; two examples would be phagolysosomes and in the plant rhizosphere.

The phase behavior of different carboxylic acids/nonionic polymer/water systems has been studied. The carboxylic acids investigated are acetic acid, propionic acid, and butyric acid. The polymers used are a linear random copolymer of ethylene oxide and propylene oxide (UCON) and ethyl(hydroxyethyl)-cellulose (EHEC). These polymers display a lower critical solution temperature (LCST) in water. The decrease of the polarity in the carboxylic acids as the carbon chain increases causes a decrease of the LCST of the system carboxylic acid/polymer/water. As a consequence of this the two-phase region expands. The experimentally determined phase diagrams can qualitatively be described and compared with a theoretical model, based on Flory-Huggins theory of polymer solubility. The cloud-point temperature of the systems decreases as the difference between the effective interaction of polymer-cosolute and cosolute-water increases. (Less)

Intercalation of linear C9–C16 carboxylates in layered Fe II–Fe III-hydroxides (green rust) via ion exchange

Asynchronous kernel analysis for binary mixture solutions of ethanol and carboxylic acids

Electrochemistry and contact angle measurements on polymer films of ω-(3-pyrrolyl)-alkanoic acids in aqueous solution

(2,6-Dichloro-4-methoxyphenyl)-(2,4-dichlorophenyl)-methyl trichloroacetimidate can be efficiently activated by TMSOTf (10∼100 mol%) to react with alcohols and carboxylic acids. Under these conditions a wide variety of alcohols can be transformed into the corresponding ethers in excellent yields with a slight excess of the trichloroacetimidate. The resulting ethers are not susceptible to typical deprotection conditions for benzyl and 4-methoxybenzyl ether groups, however, they can be conveniently deprotected by treatment with 30∼50% trifluoroacetic acid in dichloromethane. Polymer-bound (2,6-dichloro-4-alkoxyphenyl)-(2,4-dichlorophenyl)methyl trichloroacetimidate is useful for immobilization of alcohols and carboxylic acids.

Non-ideal adsorption of divalent cations on a Langmuir monolayer: A theoretical model for predicting the composition of the resulting Langmuir–Blodgett films

A metal‐free and catalytic method for the synthesis of 2‐substituted benzoxazoles and benzothiazoles from N‐protected amino acids and carboxylic acids is described. The synthesis of benzoxazole on a solid support is demonstrated by the synthesis of benzoxazole attached to a human islet amyloid polypeptide, hIAPP22–27, fragment and benzoxazole derivatives of the side chain of aspartic acid on a modified fragment of Aβ18−21 (amyloid β) peptide. The reactions proceeded through a two‐step mechanism. The coupling step is realized with a relatively new reagent, ethyl 2‐cyano‐2‐(2‐nitrobenzenesulfonyloxyimino)acetate (ortho‐NosylOXY), and the cyclization step takes place thanks to an inexpensive organocatalyst, para‐toluenesulfonic acid, under microwave irradiation. To the best of our knowledge, this is the first report of the complete synthesis of benzoxazole derivatives of a polypeptide on a resin solid support.

Aluminum anodization in an aqueous solution of formic acid and sodium vanadate leads to the formation of alumina/carbon composite films. This process was optimized by varying the concentrations of formic acid and sodium vanadate, the pH, and the processing time in constant-voltage (60–100 V) or constant-current mode. As estimated, in this electrolyte, the anodizing conditions played a critical role in forming thick, nanoporous anodic films with surprisingly high carbon content up to 17 at.%. The morphology and composition of these films were examined by scanning electron microscopy, ellipsometry, EDS mapping, and thermogravimetry coupled with mass spectrometry. For the analysis of incorporated carbon species, X-ray photoelectron and Auger spectroscopies were applied, indicating the presence of carbon in both the sp2 and the sp3 states. For these films, the Tauc plots derived from the experimental diffuse reflectance spectra revealed an unprecedentedly low bandgap (Eg) of 1.78 eV compared with the characteristic Eg values of alumina films formed in solutions of other carboxylic acids under conventional anodization conditions and visible-light absorption.

New halide-free fluxes are becoming more prevalent in electronic packaging; however, their efficacy and reactive behavior with conventional solders has not been well characterized. In this work, we examine nonaqueous halide-free flux reactions of tin (Sn)-based solder surfaces using electrochemical methods. Cyclic voltammetry was used to study reactions of Sn(II) and Sn(IV) species, x-ray photoelectron spectroscopy (XPS) was used to study surface chemistry, and chronopotentiometry was used to quantify equilibrium constants of Sn–carboxylic complexes. Reactions were investigated using carboxylic acid solutions such as adipic acid or maleic acid in polyethylene glycol. Carboxylic acid-based fluxes are practically inactive toward SnO2 removal at room temperature (25°C); however, some species are capable of removing the oxides at temperatures as high as 180°C and at pH as low as 0.1. XPS results suggest the H+ activity of the carboxylic acid is the key to removing SnO2 on Sn-based solder surfaces. Equilibrium coefficients and potential-pH diagrams are given to elucidate the influence of pH on Sn surfaces.

Tetrahedrally coordinated titanium oxides implanted into inorganic materials aid in the removal of air-based pollutants by photocatalytic reactions. We investigated the distribution and the coordination state of titanium oxides in a phase-separated glass formed by the spinodal decomposition to obtain porous glass containing tetrahedrally coordinated titanium oxides. Various glass compositions containing titanium oxides were prepared by partially replacing SiO2 with B2O3 and small amounts of TiO2 in multicomponent silicate glass compositions where a spinodal decomposition had been confirmed. Interconnected microstructures that consist of two different phases were observed in heat-treated glass samples using transmission electron microscopy and these microstructures underwent spinodal decomposition. Compositional analyses of these microstructures using energy dispersion spectroscopy revealed that the decomposed phase with higher concentration of SiO2 contains smaller amount of titanium oxides than the other phase. Thermodynamic analysis was conducted to evaluate the distribution of titanium oxides in the glass phases, formed by a phase separation in the multicomponent borosilicate glass, where glass was regarded as a super-cooled liquid phase. In the thermodynamic analysis, the calculated activity of TiO2 in the two decomposed glass phases indicated that the glass phase with higher concentration of SiO2 contains lower concentration of titanium oxides. Porous glasses containing titanium oxide were fabricated from the spinodal-decomposed borosilicate glass by leaching one of the separated phases with an acid solution. Ti K-edge X-ray absorption near edge structure spectra indicated that the porous glass contains tetrahedrally coordinated titanium oxides.

3,5-Dimethylpyrazole and halogen-containing carboxylic acids in solution give rise to equilibrium between the free molecules and 1 : 1 and 1 : 2 H-complexes. These complexes either have a ion pair-like structure with two equivalent hydrogen bonds O−⋯HN+ (1 : 1) or include homoconjugate anion with strong hydrogen bond C-O-H⋯O-C (1 : 2). At low temperatures, 2 : 1 complexes were detected. The structure and harmonic vibration frequencies of the complexes were calculated in terms of the density functional theory.

Porous glass was fabricated using spinodal decomposition in multi-component oxide glass and leaching out one of the decomposed phases with acid solution. Multi-component borosilicate glass compositions were designed for the porous glass by partially replacing SiO2 by B2O3 in silicate glass compositions where the occurrence of spinodal decomposition was confirmed. One of separated phases formed by the spinodal decomposition in the borosilicate glass was leached out with acid solution and then porous glass was obtained. The microstructure in porous glass was observed by field emission scanning electron microscopy, and the development of an interconnected porous structure was indicated. Prediction of the phase separation was attempted for multi-component borosilicate glass compositions investigated in this study by calculating the Gibbs energy of super-cooled liquid phase. It was revealed the calculated metastable liquid–liquid immiscibility boundaries in these borosilicate systems do not coincide with experimental results for the occurrence of phase separation. For the precise estimation of the miscibility gap in the multi-component oxide glasses containing B2O3, the temperature and composition dependence of Gibbs energy of liquid phase, including the super-cooled liquid state, should be optimized.

Experiment and molecular dynamics study on the mechanism for hydrophobic impregnation in cement-based materials: A case of octadecane carboxylic acid

Studies on transport properties of short chain aliphatic carboxylicacids in electrodialytic separation