Ester interchange of methyl methacrylate with fractions of higher fatty alcohols

Optimal conditions were found for preparing higher alkyl methacrylates by ester interchange of methyl methacrylate with fractions of higher alcohols.     

The electrical conductivity of polymer blends filled with carbon-black

The electrical conductivity of natural rubber/polyethylene blends filled with carbon-black is much higher than those of the individual components at the same loading level. This effect cannot be explained by a higher affinity of carbon-black for one component of the blend.     

Ethylene copolymers with Fischer-Tropsch olefins

The properties of ethylene copolymers, terpolymers and multipolymers prepared with even and uneven carbon number linear and branched α-olefins were compared. The most likely microstructures of ethylene/linear α-olefin copolymers was assigned by considering co-unit bulkiness, average crystallizable sequence lengths and thermal properties. The higher α-olefins were found to be more effective at decreasing density, but peak melting temperatures were higher. In terpolymers where lower α-olefins such as 1-butene and 1-pentene were used as comonomers, density was decreased more than the mathematical average expected from the ratio of comonomers in the terpolymers. Peak melting temperatures were also lower. Based on NMR evidence and the microstructures of the different copolymers the rationale for this occurrence could be ascribed to decreased clustering for these terpolymers. Branched α-olefins produced ethylene co- and terpolymers with significantly decreased densities as compared to the linear α-olefins. Impact strength of these polymers was also substantially higher, even at low comonomer content. Thermal evidence indicates that the microstructure of the co- and terpolymers containing branched α-olefins are very similar to that of the copolymers prepared with linear α-olefins of the same carbon number.     

Dried biomass of green algae and its matrix matching with green parts of higher plants

Literature data for the content of matrix elements in dry biomass of green algae have been compared with those for green parts of higher plants. The data were evaluated by means of frequency histograms and box-and-whisker plots. With two exceptions (Fe, P), the spread of the data values for a given element was broader for higher plants than for algae. Distribution of the data was asymmetric, in most cases with long right-hand tails. All outliers found (average 5.6% for algae, 9.1% for higher plants) lay above the bulk of the data values. In all cases, there was either partial or (mostly) complete overlap of the ranges for algae with those for higher plants. While the question of matrix-matching of reference materials prepared from algal biomass with samples from green parts of higher plants can exhaustively be answered only after a similar comparison of the composition of matrix compounds, the content of the main matrix elements is certainly not doubtful.     

One-pot synthesis of hybrid macrocyclic pentamers with variable functionalizations around the periphery

Rather than four- or six-residue macrocylces, one-pot macrocyclization allows for the highly selective formation of five-residue macrocycles rigidified by intramolecular hydrogen bonds. Variable functionalizations around the pentameric periphery were achieved by reacting monomers with higher oligomers bearing different exterior side chains. The formation of these hybrid pentamers suggests a chain-growth mechanism for the one-pot macrocyclization where the successive addition of monomers onto higher oligomers is faster than those between two monomers or two higher oligomers.     

Solvent-free condensation of arylacetonitrile with aldehydes

The condensation of a series of arylacetonitriles with aldehydes can be carried out by mixing equivalent amounts of reagents with neat powdered KOH at room temperature for 3-60 min depending on the aldehyde steric hindrance. At higher temperature (110 °C), yields were generally higher and purity increased within very short reaction times (1-5 min). With pentamethylphenylacetonitrile, a phase transfer agent was necessary to give a satisfactory yield.     

Polymers with improved flammability characteristics. I. Phenolphthalein-related homopolymers

Improved fire resistance occurs for phenolphthalein-related polycarbonates and polyesters compared to bisphenol-A polymers and emphasizes the importance of polymer composition and polymer structure in affecting the flammability of a polymer. Phenolphthalein-related polymers are able to produce a higher degree of crosslinking during pyrolysis which subsequently leads to higher char yields. The correlations between oxygen index and char yield for various polymers are obtained and discussed. Polycarbonates and polyamides usually show higher oxygen indices than the corresponding polyesters of related structures. This indicates that the nature of the pyrolysis products has a measurable effect on the flammability of a specific polymer. Among many factors, polycarbonates should release more CO₂ from the breakdown of the carbonate group, and polyamides should produce relatively nonflammable nitrogen-containing products during pyrolysis, thus accounting in part for these results.     

Ion chromatographic system with a novel switching suppression device

Ion chromatography (IC) has been a powerful tool for measuring ionic species in environmental samples such as tap, river and drain waters. Suppressor modules (membrane and disposable column types) have been used for reducing the background of a baseline. A new type of suppressor device, which has a suppressor resin and switching valve was developed. Fresh ionic resin is introduced into a groove for each analysis to perform the suppression of the working eluent. The eluent composition for obtaining higher sensitivity and better resolutions among ionic species and carbonate ion was also investigated. Although carbonate buffers are used for ion separation in general, the separation of carbonate ion from other ions was not achieved. A borate eluent resulted in good resolutions and higher sensitivity. A new column was also developed for obtaining higher column efficiency and resolution. The optimization of anion separation using a new IC system (IC-2001) that consists of a new suppressor device, an anion-exchange column (TSKgel SuperIC-Anion, 150x4.6 mm), an autosampler, a conductivity cell and a pump in a compact module is described.     

Nuclear fluorination of 3,5-diarylisoxazoles with Selectfluor

C-4 Fluorination of a series of 3,5-diarylisoxazoles has been accomplished using the N-F reagent Selectfluor^®. With substrates containing neutral or activating substituents on the 5-phenyl ring, acetonitrile at room temperature or at reflux could be used as solvent. However, when deactivating substituents were present, a higher reaction temperature was required for which sulfolane was found to be a good solvent. At this higher temperature, a unique trifluorination of the isoxazole nucleus by an addition mechanism occurred as a side reaction.     

A SAPO-11 Silicoaluminophosphate Molecular Sieve with Stable Crystal Structure

A SAPO-11 silicoaluminophosphate molecular sieve with stable crystal structure was synthesized for the first time. After removing template by calcination, its crystal space group still retains Icm2 which the as-synthesized has. The catalyst deriving from the present SAPO-I 1 materials shows higher isomerization selectivity and higher paraffin hydroisomerization yield than those reported elsewhere.     

Solvent-free reactions with hypervalent iodine reagents

[reaction: see text] We describe solvent-free reactions for the synthesis of hypervalent iodine reagents and their use in solid-state reactions. Improved yields and higher purities of the products are observed.     

Analysis of multiplex PCR fragments with PMMA microchip

Microchip electrophoresis is a promising technique for analysis of bio-molecules. It has the advantages of fast analysis, high sensitivity, high resolution and low-cost of samples. Plastic chip has the potential of mass production for clinical use for its advantages in biocompatibility and low cost. In this work, the method for fabrication of poly(methyl methacrylate) (PMMA) chip was described, and conditions for DNA separation were investigated with the chip. The PMMA microchip was used for detection of multiplex PCR products of 18 and 36 cases with SARS and hepatitis B virus infection under optimized separation conditions. Microchip electrophoresis showed higher sensitivity, higher resolution and less time consumption when compared with gel electrophoresis. The microchip electrophoresis with PMMA chip provided a rapid, sensitive and reliable method for analysis of multiplex PCR products.     

Interaction of dihydroxybenzenes with pyrogenic silica

The chemisorption of pyrocatechnol and resorcinol on the surface of pyrogenic (fumed) silica has been studied experimentally and theoretically. The dependence of sorption on the silica pretreatment temperature has been investigated. Pyrocatechol has a higher reactivity, as evidenced by the lower temperature for maximum chemisorption in comparison with resorcinol. The higher reactivity of the pyrocatechol is due to the possibility of participation of the second OH group of the ortho isomer in the reaction — by double H⁺ transfer in a many-center transition state with an S_Ni-Si mechanism.     

Protein association with circular DNA: rate enhancement by nonspecific binding

An analytical solution for the nonspecific-binding-facilitated diffusion-controlled rate of association of a protein with a specific site on a circular DNA is derived. Nonspecific binding is modeled by a short-range attractive surface potential. The protein undergoes diffusion in the bulk solution and in the surface layer. The association rate for a circular DNA is compared to the counterpart for a linear DNA, in which the ends of the surface layer are treated as reflecting. As expected, when the DNA length is long, the shape of the DNA does not affect the association rate. For a shorter length, the association rate for the linear DNA is modestly higher than the circular counterpart. The higher rate of the linear DNA is possibly due to its more open shape, which affords it a higher ability to draw the protein from the bulk to its surface. The analytical solution is verified by Brownian dynamics simulations.     

Biphasic Catalytic Hydroformylation of 1-Dodecene in Micellar System with Cationic Gemini Surfactants

The promotion effect of cationic gemini surfactants for the hydroformylation of 1-dodecene in the organic/aqueous biphasic catalytic system is reported. The hydroformylation reaction in the presence of gemini surfactant occurred with higher turnover frequency and higher selectivity for linear aldehyde than using conventional monomeric surfactant CTAB.     

Enantioselective uptake of amino acid with overoxidized polypyrrole colloid templated with L-lactate

An overoxidized polypyrrole colloid, which can recognise enantiomers of amino acids has been prepared by a newly developed molecular imprinting technique. A polypyrrole colloid, which had been polymerised from a mixture of pyrrole (monomer), polyvinylpyrrolidone (steric stabiliser), peroxodisulfate (oxidant) and L-lactate (dopant), was overoxidized to create a dopant-complementary cavity. The enantioselectivity of the overoxidized colloid was evaluated by comparing the uptake of L-alanine and L-cysteine with that of the respective D-enantiomers. The L/D uptake ratios for these amino acids were about 2, while phenylalanine showed suppressed uptake for both the enantiomers. The absence of phenylalanine uptake can be explained in terms of the molecular size, which is too large to be accommodated by the cavity created by L-lactate. In contrast, a colloid templated with L-phenyllactate took up L-phenylalanine with a higher enantioselectivity of about 7. A colloid templated with L-lactate was applied to surface chirality analysis through enantioselective adsorption on cysteine-modified gold surfaces. Quartz microbalance experiments and scanning electron microscope observation of the gold surface revealed that the colloidal particle has higher affinity to a surface modified with L-cysteine than to one modified with D-cysteine.     

Anthocyanin Color Stabilization by Host-Guest Complexation with p-Sulfonatocalix[n]arenes

Flavylium-based compounds in their acidic and cationic form bring color to aqueous solutions, while under slightly acidic or neutral conditions they commonly bring discoloration. Selective host-guest complexation between water-soluble p-sulfonatocalix[n]arenes (SCn) macrocycles and the flavylium cationic species can increase the stability of the colored form, expanding its domain over the pH scale. The association constants between SCn and the cationic (acid) and neutral basic forms of flavylium-based compounds were determined through UV-Vis host-guest titrations at different pH values. The affinity of the hosts for synthetic chromophore was found to be higher than for a natural anthocyanin (Oenin). The higher affinity of SC4 for the synthetic flavylium was confirmed by ¹H NMR showing a preferential interaction of the flavylium phenyl ring with the host cavity. In contrast with its synthetic counterpart, the flavylium substitution pattern in the anthocyanin seems to limit the inclusion of the guest in the host’s binding pocket. In this case, the higher affinity was observed for the octamer (SC8) likely due to its larger cavity and higher number of negatively charged sulfonate groups.     

Principal component analysis with boundary constraints

Observed data often belong to some specific intervals of values (for instance in case of percentages or proportions) or are higher (lower) than pre‐specified values (for instance, chemical concentrations are higher than zero). The use of classical principal component analysis (PCA) may lead to extract components such that the reconstructed data take unfeasible values. In order to cope with this problem, a constrained generalization of PCA is proposed. The new technique, called bounded principal component analysis (B‐PCA), detects components such that the reconstructed data are constrained to belong to some pre‐specified bounds. This is done by implementing a row‐wise alternating least squares (ALS) algorithm, which exploits the potentialities of the least squares with inequality (LSI) algorithm. The results of a simulation study and two applications to bounded data are discussed for evaluating how the method and the algorithm for solving it work in practice. Copyright © 2007 John Wiley & Sons, Ltd.     

Photolysis of benzophenone with two-step two-laser excitation

The first laser excites a molecule to a lower triplet state and another sequential laser excites it resonantly to higher triplet states or makes it ionization. This two-step two-laser method provides a novel way to study the electron transfer or charge transfer of excited molecules. The higher excited benzophenone and its radical cation can be observed under the time-resolved absorption method when it was excited to lower triplet state by one laser and another one exciting it to higher triplet states resonantly. The higher excited benzophenone molecules undergoing inter-molecular hydrogen abstraction with iso-propylalcohol molecules are faster than the lower ones.     

Hyperbranched ferrocenyl polymer film with high charge transport efficiency

The electrochemical behaviors of hyperbranched poly(ferrocenyl-methylsilane) (HPFMS) and linear oligo(ferrocenyldimethylsilane) (LOFS) films were studied systematically by cyclic voltammetry and chronocoulometry under different polymer coverage and solvents. Both poly(ferrocenylsilanes) show stable cyclic voltammographs in LiClO 4 solutions. Compared with LOFS films, HPFMS films exhibit higher charge transport efficiency because of their hyperbranched structure: peak current ( i p) and apparent diffusion coefficient ( D app) for HPFMS films are larger than those for LOFS films, especially at high polymer coverage (3.8 x 10 (-11) vs 3.9 x 10 (-12) cm (2)/s for HPFMS and LOFS film at the coverage of 2.1 x 10 (-6) mol Fc/cm (2)). The conceptual models of electrode processes for HPFMS and LOFS films were proposed to account for higher charge transport efficiency of HPFMS films. It is also found that a solvent with the appropriate solubility parameter and polarity, lower viscosity, and higher dielectric constant is in favor of charge transport through polymer films, which is consistent with the proposed model of electrode process for HPFMS films. These results imply that hyperbranched ferrocenyl polymers have the potential to be excellent chemical sensor materials with convenient synthesis and high sensitivity.