Proton‐conducting electrolytes based on silylated and sulfonated polyetheretherketone: Synthesis and characterization

A derivative of polyetheretherketone (PEEK) having sulfonic acid groups and silicon‐containing substituents covalently bound to the aromatic backbone has been prepared as proton‐exchange membrane material. The polymer 4 (PhSiSPEEK) has been synthesized via (i) sulfonation of PEEK up to 0.9 degree of sulfonation (DS, the number of sulfonic groups per repeat unit), (ii) conversion of sulfonated PEEK 1 (SPEEK09) into sulfonyl chlorinated derivative 2 (PEEKSO₂Cl), (iii) lithiation of 2 and subsequent addition of PhSiCl₃, followed by hydrolysis. The chemical structure of the synthesized polymers has been investigated by ¹H NMR and ¹³C NMR and ATR/FTIR spectroscopy and their thermal stability has been evaluated by thermogravimetric analysis. The presence of inorganic moieties increases the thermal stability of 4 with respect to the sulfonated and not silylated product. Despite its very high DS, PhSiSPEEK is insoluble in water but does not possess the plastic properties needed to be used as an electrolyte membrane. Blend membranes made of SPEEK05 (DS = 0.5) and containing 10 and 25 wt % of 4 (DS = 0.9, degree of silylation DSi = 0.1) have been prepared and characterized by water uptake measurements and electrochemical impedance spectroscopy. The combination of the two functionalized polymers having different properties allows to obtain proton‐conducting electrolytes that are potential candidates for fuel cells applications. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 2178–2186, 2010     

The cavity elongation effect. Calorimetric studies of the complexes of long-chain carboxylic acids with methyl-α-cyclodextrin in aqueous solutions

The formation of complexes between methyl-α-cyclodextrin (MαCD) and monocarboxylic acids from C₅ to C₁₂ or cycloalkanols has been studied calorimetrically at 298 K in aqueous phosphate buffer, pH 11.3. The forces involved in the association process are discussed according to the signs and values of the thermodynamic parameters obtained: association enthalpy, constant, Gibbs energy and entropy. Methyl-α-cyclodextrin forms 1:1 inclusion complexes with monocarboxylic acids, characterized by a monotonous increase in the values of enthalpies and association constants at increasing alkyl chain length. Association is characterized by negative enthalpies and by positive entropies: that determines large association constants. That behaviour is compared to the unusual trend in the values of the association constants shown by the parent α-cyclodextrin interacting␣with the same monocarboxylic acids. The model proposed to rationalize the present data provides a cavity elongation effect. Namely, because of the presence of the methyl groups on the outside, the cavity behaves as it were deeper than that of the parent cyclodextrin. The association with cycloalkanols—cyclohexanol, cycloheptanol, cyclooctanol and 1-cylohexyl-ethanol—is characterized by lower entropies, as determined by the␣enhanced negative contribution originating from the␣tighter fit of the guest into the cavity.     

Time‐Resolved In Situ Synchrotron X‐ray Study and Large‐Scale Production of Magnetite Nanoparticles in Supercritical Water

A general solution : In situ synchrotron X‐ray scattering in a high‐pressure pulsed injection reactor (see picture) shows that magnetite nucleation and growth are temporally separated. Gram‐scale crystalline, pure phase, superparamagnetic magnetite nanoparticles were synthesized without surfactants in supercritical water in less than one hour using a laboratory‐scale continuous‐flow reactor.

     

Fast catalytic hydroxylation of hydrocarbons with ruthenium porphyrins

Ruthenium porphyrin complexes such as carbonylruthenium(II) tetrakispentafluorophenylporphyrin [Ru(II)(TPFPP)(CO)] were found to be efficient catalysts for the hydroxylation of alkanes in the presence of 2,6-dichloropyridine N-oxide as the oxidant under mild, nonacidic conditions. Up to 14 800 turnovers (TO) and rates of 800 TO/min were obtained for the hydroxylation of adamantane. The hydroxylation of cis-decalin afforded cis-9-decalol and cis-decalin-9,10-diol, exclusively, thus, excluding a long-lived radicals mechanism. The kinetics of product evolution in a typical catalytic oxygenation showed an initial induction period followed by a fast, apparently zero-order phase with maximum rates and high efficiencies. Deuterium isotope effects (kH/kD) in the range of 4.2-6.4 were found for the hydroxylation of alkanes. A Hammett treatment of the data for the oxidation of para-substituted toluene derivatives showed a linear correlation with a highly negative rho+ value of -2.0. On the basis of kinetic and spectroscopic evidence, Ru(VI)(TPFPP)(O)2, Ru(II)(TPFPP)(CO), and Ru(IV)(TPFPP)Cl2 observed during catalysis were ruled out as candidates for the active catalyst responsible for the high efficiencies and turnover rates in the oxidation reactions. The fastest rates of adamantane hydroxylation with 2,6-dichloropyridine N-oxide were achieved by the reductive activation of Ru(IV)(TPFPP)Cl2 with a zinc amalgam. This redox activation is consistent with the formation of an active Ru(III) intermediate in situ by a one-electron reduction of the Ru(IV) porphyrin. EPR spectra characteristic of Ru(III) have been observed upon the reduction of Ru(IV)(TPFPP)Cl2 with a zinc amalgam. In the adamantane oxidation mediated with Ru(III)(TPFPP)(OEt), it was found that, during this process, the Ru(III) porphyrin was gradually converted to a dioxoRu(VI) porphyrin. Concomitant with this conversion, the reaction rates decreased. Catalyst activation was also stimulated by autoxidation of the solvent CH2Cl2. On the basis of these data, a mechanism is proposed that incorporates a "fast" cycle involving metastable Ru(III) and oxoRu(V) intermediates and a "slow" oxidation cycle, mediated by oxoRu(IV) and trans-dioxoRu(VI) porphyrin complexes.     

Hybrid polyoxotungstates as second-generation POM-based catalysts for microwave-assisted H2O2 activation

[structure: see text] Organic-inorganic hybrids synthesized from lacunary polyoxotungstates (POMs) have been screened as oxidation catalysts with H2O2 under MW irradiation. Yields up to 99% have been obtained in 25-50 min depending both on the POM structure and on the organic moiety. The reaction scope, optimized with the best performing catalyst [gamma-SiW10O36(PhPO)2]4-, includes epoxidation of terminal and internal double bonds, alcohol oxidation, and sulfoxidation, as well as oxygen transfer to electron-deficient substrates as chalcone, ketones, and sulfoxides.     

Surface behavior and molecular recognition in DNA microarrays from N,N-dimethylacrylamide terpolymers with activated esters as linking groups

A series of terpolymers made of DMA, NAS and MAPS were synthesized by free radical copolymerization and used as functional coatings for the fabrication of glass slide DNA microarrays. The surface properties of coated glass slides were investigated through contact angle measurements, ellipsometry and atomic force microscopy. The terpolymer molecular weight showed a moderate effect on surface tension (gamma(s) = 56-62 mN x m(-1)), but no clear effect on polymeric layer thickness (5-8 nm) and roughness. Hybridization experiments with amine-functionalized oligonucleotides gave the best fluorescence intensity results for microarrays coated with intermediate-molecular-weight terpolymers. Finally, an accelerated ageing test of the microarray in a humidity chamber showed a nice relationship between decay curves of contact angle against water and fluorescence intensity.     

Hybrid multi-objective Bayesian estimation of distribution algorithm: a comparative analysis for the multi-objective knapsack problem

Nowadays, a number of metaheuristics have been developed for efficiently solving multi-objective optimization problems. Estimation of distribution algorithms are a special class of metaheuristic that intensively apply probabilistic modeling and, as well as local search methods, are widely used to make the search more efficient. In this paper, we apply a Hybrid Multi-objective Bayesian Estimation of Distribution Algorithm (HMOBEDA) in multi and many objective scenarios by modeling the joint probability of decision variables, objectives, and the configuration parameters of an embedded local search (LS). We analyze the benefits of the online configuration of LS parameters by comparing the proposed approach with LS off-line versions using instances of the multi-objective knapsack problem with two to five and eight objectives. HMOBEDA is also compared with five advanced evolutionary methods using the same instances. Results show that HMOBEDA outperforms the other approaches including those with off-line configuration. HMOBEDA not only provides the best value for hypervolume indicator and IGD metric in most of the cases, but it also computes a very diverse solutions set close to the estimated Pareto front.     

Total synthesis of anthocyanidins via Heck reaction

Anthocyanidin moiety was obtained by cyclization of a 2-hydroxychalcone prepared by the Heck approach to the synthesis of flavonoids. 1-(3,4-dimethoxyphenyl)-prop-2-en-1-one has been used as a coupling partner along with o-acetoxyiodobenzene in the Heck reaction.     

Investigation into the allylation reactions of aldehydes promoted by the CeCl3.7H2O-NaI system as a Lewis acid

The Lewis acid promoted allylation of aldehydes has become an important carbon-carbon bond forming reaction in organic chemistry. In this context, we have developed an alternative over existing catalytic processes, wherein aldehydes are subject in acetonitrile to reaction of allylation with allyltributylstannane in the presence of 1.0 equiv of cerium(III) chloride heptahydrate (CeCl(3).7H(2)O), an inexpensive and mild Lewis acid. The allylation has been accelerated by using an inorganic iodide as a cocatalyst, and various iodide salts were examined. The procedure must use allylstannane reagent instead of allylsilane reagent, desirable for environmental reasons, but high chemoselectivity was observed, and this is opposite the results obtained with other classical Lewis acids such as TiCl(4) and Et(2)O.BF(3).