Iodination of stable aromatic diazonium salt using crosslinked poly (4‐vinylpyridine)‐supported iodide

In this article, a series of carboxylated acrylate copolymer latices were prepared based on the semicontinuous emulsion polymerization via the pure monomer dropwise manner with three different kinds of carboxylic monomers in presence of reactive emulsifier. The effects of the carboxylic monomers [acrylic acid, methacrylic acid, and monobutyl itaconate (MBI)] on the conversion and the properties of acrylate latices and films have been investigated. The carboxylic groups ( COOH) distribution of these three kinds of latices were investigated as well. The results show that the concentration of surface  COOH (C_S) and embedded  COOH (C_b) both increase with the increase of the amount of carboxylic monomers. It shows that MBI, the most hydrophobic of the three carboxylic monomers used, tends to be concentrated inside the particle core, and the latex particles have a narrow size distribution. The results of common stability test have demonstrated that the stability of the latex is satisfactory. Moreover, the water absorption and the acid and alkaline resistance of the latex depend on the kind of carboxylic monomer. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Simple and facile synthesis of aryl benzoates from stabilized arenediazonium tetrafluoroborate using a recyclable polymer-supported benzoate ion

Temperature-responsive P(NIPAM-co-HMAM)-b-PEO-b-P(NIPAM-co-HMAM) triblock copolymers were synthesized by an atomic transfer radical polymerization (ATRP) method without freeze?Cpump?Cthaw cycles. The composition, structure, and molecular weight of the synthesized block copolymer were characterized by ¹?H NMR and GPC. The phase transitions induced by temperature for different copolymers in dilute aqueous solutions have been studied using transmittance measurements, laser particle size measurements, viscosity analysis, and surface tension measurement, which showed that the HMAM content and the PEO (or PEG) chain length in the synthesized triblock copolymer affects the copolymer??s lower critical solution temperature (LCST). The micellization behavior of each temperature-responsive triblock copolymer was investigated by fluorescence probe measurements and transmission electron microscopy (TEM), which showed that the triblock copolymers form stable micelles above the LCST. The introduction of the HMAM component and the formation of micelles represent the first steps in the development of an injectable gel that forms in situ through chemical and physical crosslinking.     

Gender,web presence and scientific productivity in nanoscience and nanotechnology

Digital and scientific realms are commonly believed to be gendered. The wide pervasiveness of e-science may result in an interaction between the scientific and digital gender divides, increasing the disparities against women. Selecting web-presence as a manifestation of web activity, and applying a quasi-experimental scientometric method, the present study aims to investigate the effects of the interaction, if any, on web-present females and males compared to web-absent ones in Nanoscience and Nanotechnology. The results show that the web-present Nanoscientists are not necessarily superior in their scientific production, though they are higher in their recognition. The web-present females and males are equal in their numbers and productions. Although the female web-present are found to be equal in their recognition to their male counterparts, there is a significant difference between the web-present and web-absent males in this regard, signifying the higher impact of the web on males’ recognition.     

Diazotization–cyanation of aromatic amines with crosslinked poly(4-vinylpyridine)-supported cyanide ions

A simple, mild, and efficient method for the cyanation of stable arenediazonium salts was developed with polymer-supported cyanide. Arenediazonium hydrogen sulfate (Ar N₂⁺HSO₄⁻) was obtained by the reaction between a primary aryl amine and sodium nitrite in the presence of concentrated sulfuric acid (H₂SO₄) at low temperature (0–5°C). By an ion-exchange reaction between Ar N₂⁺HSO₄⁻ and NaBF₄, the stable arenediazonium tetrafluoroborate, Ar N₂⁺BF₄⁻, was prepared. Ar N₂⁺BF₄⁻ was then converted to aryl nitrile with crosslinked poly(4-vinylpyridine) supported cyanide ion in acetonitrile at room temperature. The spent polymeric reagent was regenerated and reused several times without any loss in its activity. This procedure offered advantages, including a higher isolated yield, shorter reaction time, and simple reaction workup. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Photopolymerization behavior and phase separation effects in novel polymer dispersed liquid crystal mixture based on urethane trimethacrylate monomer

Polymer dispersed liquid crystals (PDLCs) are often formed by polymer induced phase separation, based on photopolymerization of multifunctional acrylate monomers. The emerged morphology is controlled by the interplay between polymerization rate and phase separation dynamics, which depends on different parameters such as monomer structure and functionality. In this work, a new PDLC formulation containing urethane trimethacrylate (UTMA) monomer is introduced, which has different molecular weight evolution, polymer gel point, and polymerization kinetics in comparison with some common ester acrylate (such as TMPTA and DPHPA) based PDLC compositions. UTMA is synthesized and characterized by Fourier transform infrared, ¹H‐NMR, and ¹³C‐NMR spectroscopic techniques. Simultaneous examination of polymer evolution and LC phase separation by real‐time infrared spectroscopy shows that the UTMA based PDLC, which contains trifunctional urethane acrylate monomer, has greater amount of bond conversion, polymerization rate, and liquid crystal (LC) phase separation in comparison with TMPTA based PDLC. In spite of the acrylate monomers, which show gel point conversions as low as 1.83–5.72%, UTMA reaches to its maximum rate at 19.5% conversion, which causes higher phase separation and therefore greater LC domain size. The experimental results are explained more precisely by means of SEM and optical microscopy analyses. The results are confirmed by electro‐optics measurements. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Adsorption of phenol onto rice straw biowaste for water purification

The adsorption technique has been studied using waste rice straw to adsorb phenol from aqueous solutions at room temperature. Batch adsorption studies were carried out under varying experimental conditions of contact time, operational temperature, pH of phenol solution, initial phenol concentration, adsorbent dose, and particle size. The time to reach equilibrium was found to be 3?h. Results showed that the equilibrium data for phenol-sorbent systems fitted the Freundlich model and Langmuir model within the concentration range studied. Adsorbed phenol could be regenerated by desorption with the help of 1M NaOH. The studies showed that the rice straw can be used as an efficient adsorbent material for removal of phenol and phenolic compounds from water and wastewater.     

Mu-trap for the SALDI-MS screening of organic compounds prior to LC/MS analysis

A procedure for rapidly screening and quantitatively analyzing organic molecules is presented, in which a miniaturized solid-phase extraction (SPE) cartridge containing 0.6 mg of graphitized carbon black (the GCB-mu-trap) is used for sample pretreatment. Then surface-assisted laser desorption ionization time-of-flight mass spectrometry (SALDI-TOF-MS) screening is followed by liquid chromatography/mass spectrometry (LC/MS) for robust quantitative analysis of samples containing analytes of interest. Liquid samples with volumes up to 100 mL were extracted using the GCB-mu-trap, and SALDI screening was performed by transferring a few particles of the GCB 4 sorbent from the mu-trap onto a stainless steel plate. Analytes were then simply ionized and desorbed by irradiating the GCB 4 particles without any further pretreatment. GCB 4 was found to be an excellent surface for the SALDI analysis of small molecules, providing spectra with very clean backgrounds. The small size of the cartridge (micropipet filter tip) results in enrichment of the analytes on a small surface area, affording low SALDI-TOF-MS detection limits. Furthermore, the removal of just a few particles from the mu-trap does not significantly affect the subsequent quantitative determination. This approach offers considerable reductions in analytical costs by eliminating unnecessary SPE-LC/MS analyses.     

Modelling the freezing of butter

Butter is a water-in-oil emulsion so its behaviour during freezing is very different from that of most food products, for which water forms a continuous phase. The release of latent heat during freezing is controlled as much by the rate of crystallization of water in each of the water droplets as by the rate of heat transfer. Measurements of the freezing of butter show that the release of latent heat from the freezing water depends on the degree of supercooling, which, in turn, depends on the cooling medium temperature, the size of the butter item, the packaging and the type of butter. Four modelling approaches were tested against the experimental data collected for a 25 kg block of butter. A “sensible heat only model” accurately predicted the butter temperature until temperatures at which water freezing becomes significant were reached. An “equilibrium thermal properties model” predicted a temperature plateau near the initial freezing point of the butter in a manner that was inconsistent with the measured data. A third model used a stochastic approach to ice nucleation based on supercooling using classical homogeneous nucleation theory. The predicted temperatures showed that supercooling-driven nucleation alone is not sufficient to predict the freezing behaviour of butter. A fourth approach took account of time-dependent nucleation and ice crystal growth kinetics using classical Avrami crystallization theory. The relationship between the ice crystal growth rate and the supersaturation was assumed to be linear. The model predicted the experimental data accurately, particularly by predicting the slow rebound in the temperature following supercooling that is found when freezing butter under some conditions.