Carboxylic acids accelerate acidic environment-mediated nanoceria dissolution

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.

Relationship between powder properties and bending strengths of the sintered magnesium oxide (MgO) specimens was examined using seven kinds of MgO powders prepared by a vapour-phase oxidation process; the average primary particle sizes were 11, 25, 32, 44, 57, 107 and 261 nm. These compressed powders (specimens) were fired at 1600 or 1700 °C for 1 to 15 h. Although the densification behaviours of the specimens varied with the primary particle size of the starting powders, the relative densities of the specimens fired at 1700 °C for 5 h were all in the range of 97–98%. The relationships between bending strengths and grain sizes of these sintered specimens could be classified into two categories, according to the primary particle size of the starting powder: (i) at and below 32 nm and (ii) 44–261 nm. In range (i), the bending strengths of the sintered specimens were as low as ∼ 120 MPa; the grain size was reduced from 50.7 to 35.8 μm as the primary particle size decreased from 32 to 11 nm. In range (ii), as the primary particle size increased from 44 to 261 nm, the bending strength of the sintered specimen was enhanced from 162 to 183 MPa, while the grain size was reduced from 28.3 to 13.7 μm.

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)

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.

A phenomenological model for predicting the size of soot primary particles emitted from an aero-engine combustor

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.

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.

Out-of-equilibrium phase transitions driven by dissipation of chemical energy are a common mechanism for morphological organization and temporal programming in biology. Inspired by this, dissipative self-assembly utilizes chemical reaction networks (CRNs) that consume high-energy molecules (chemical fuels) to generate transient structures and functionality. While a wide range of chemical fuels and building blocks are now available for chemically fueled systems, so far little attention has been paid to the phase-separation process itself. Herein, we investigate the chemically fueled spinodal decomposition of poly(norbornene dicarboxylic acid) (PNDAc) solution, which is driven by a cyclic chemical reaction network. Our analysis encompasses both the molecular level in terms of the CRN, but also the phase separation process. We investigate the morphology of formed domains, as well as the kinetics and mechanism of domain growth, and develop a kinetic/thermodynamic hybrid model to not only rationalize the dependence of the system on fuel concentration and pH, but also open pathways towards predictive design of future fueled polymer systems.

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

Radiopaque dental adhesives: Dispersion of flame-made Ta 2O 5/SiO 2 nanoparticles in methacrylic matrices