Effect of a Nanoclay on the Mechanical,Thermal and Flame Retardant Properties of Rigid Polyurethane Foam

Water blown rigid polyurethane foams (PUF) with organoclay/organically modified nanoclay (ONC) were prepared and their properties such as density, mechanical, morphological, insulation, thermal and flame retardant properties were studied. In this investigation, the ONC content was varied from 1 to 10 parts per hundred of polyol (php) by weight. It was observed that the compressive strength of ONC filled PUF increased up to 3 php of ONC loading and then it decreased. Wide angle X-ray diffraction and transmission electron microscopy studies indicated the exfoliated dispersion of ONC in PUF. The thermal conductivity of ONC filled PUF decreases up to 5 php and then increases. The glass transition temperature (Tg) of PUF decreases on loading of ONC. The TGA analysis shows that there is slight increase in degradation temperature with increase in ONC loading. The flame retardant properties (LOI and flame spread rate) are improved slightly on addition (3 php) of ONC filled PUF.     

Miscibility and Thermal Behavior of Pullulan/Polyacrylamide Blends

Blends of Pullulan (PU) and Polyacrylamide (PAM) having biomedical applications were prepared and characterized in order to evaluate the miscibility of natural component with the synthetic one. Blends with different composition ratios were prepared using water as common solvent. Viscosity, ultrasonic velocity and density were measured at 30 and 40°C. Furthermore, the blend films were prepared by a solution casting method and analyzed by DSC, FTIR and TGA methods. Results of ultrasonic and density methods revealed the semi-miscibility of the blend. Using viscosity data, interaction parameters (Chee's ‘μ’ and Sun's ‘α’) were computed. The values confirmed that the blend is miscible when the Pullulan content is less than 20% in the blend. Change in temperature had no effect on the miscibility nature of the blends. Intermolecular interactions of hydrogen bonding type were confirmed by DSC and FTIR methods. Thermal behavior of blends was investigated using TGA method.     

Rapid Biosynthesis of Silver Nanoparticles Using Areca Nut (Areca catechu) Extract Under Microwave-Assistance

In this research paper, we report on the rapid synthesis of silver nanoparticles using dried areca nut (Areca catechu). The microwave exposed aqueous areca nut powder when treated with the aqueous silver salt solution yielded irregular shaped silver nanoparticles. The formation and morphology of the nanoparticles are studied using UV–visible spectroscopy, field emission scanning electron microscopy, transmission electron microscopy and atomic force microscopy. The X-ray diffraction studies and energy dispersive X-ray analysis indicate that the particles are crystalline in nature. The understanding of capping of biological moiety is derived from Fourier transform infrared spectroscopy and the thermogravimetric analysis. The green chemistry approach for the synthesis of silver nanoparticles is modest, amenable for large scale commercial production. Further the biologically synthesized silver nanoparticles are known for their potential antibacterial activity.     

Convenient Synthesis of 1,3,6-Triene Systems Through Alkylation of 3-Methyl-3-sulfolene.

Abstract: Various 1,3,6-triene systems have been synthesised through alkylation of 3-methyl-3-sulfolene with conjugated aldehydes followed by silylation and subsequent desulfonylation. A new route to synthesis of (+/?)-α-chamigrene, isofokienol and 5-hydroxy-α-farnesene has been described.     

Co‐ and Counterion Effect on the Micellization Characteristics of Dodecylpyridinium Chloride

Micellization parameters, critical micelle concentration (cmc), degree of counterion dissociation (α), aggregation number (n), critical packing parameter, and hydrophobic core volume of Dodecylpyridinium chloride (DPC) micelles were determined in presence of varying concentrations of sodium chloride (NaCl), sodium acetate (SAc), sodium propionate (SPr), ethylammonium chloride (EACl), diethylammonium chloride (DEACl), tetraethylammonium chloride (TEACl), and propylammonium chloride (PACl) through conductometric investigations at 298.15 K. The resulting data suggests that both counter and coions affect the cmc values‐cmc depressing tendency of the salts varies in order PACl≈NaCl>EACl>DEACl>TEACl>SPr>SAc, while the degree of counterion dissociation is dependent on the nature and concentration range of the added salt. Increasing salt concentration increases the relative hydrophobic volume of the micelles and coion has not much effect on aggregation number.     

Palladium complex in a room temperature ionic liquid: a convenient recyclable reagent for catalytic oxidation

Palladium (Pd)-catalyzed carbonylation of alcohols proceeds in ionic liquid (IL) media (1-ethyl-3-methylimidazolium hexafluorophosphate). Carbonylation of primary/secondary alcohols to aldehydes/ketones was greatly accelerated by the use of a Pd-based catalyst in the presence of NaOCl as an oxidant. The catalyst was more easier to recycle in the IL [Emim]PF₆ with an equal-proportioned CH₂Cl₂ than in the single CH₂Cl₂ or IL.     

[2+3] Amide Cages by Oxidation of [2+3] Imine Cages – Revisiting Molecular Hosts for Highly Efficient Nitrate Binding

The pollution of groundwater with nitrate is a serious issue because nitrate can cause several diseases such as methemoglobinemia or cancer. Therefore, selective removal of nitrate by efficient binding to supramolecular hosts is highly desired. Here we describe how to make [2+3] amide cages in very high to quantitative yields by applying an optimized Pinnick oxidation protocol for the conversion of corresponding imine cages. By NMR titration experiments of the eight different [2+3] amide cages with nitrate, chloride and hydrogen sulfate we identified one cage with an unprecedented high selectivity towards nitrate binding vs. chloride (S=705) or hydrogensulfate (S>13500) in CD₂Cl₂/CD₃CN (1 : 3). NMR experiments as well as single-crystal structure comparison of host-guest complexes give insight into structure-property-relationships.     

Atomic Layer Deposited Ti2O3 Thin Films

Ti₂O₃ thin films have been prepared through atomic layer deposition and subjected to electrical resistivity measurements as a function of temperature. The as-prepared films were stable for up to three weeks. In Ti₂O₃ thin films, the insulator-metal transition is observed at ∼80 K, with nearly 3–4 orders of magnitude change in resistivity. The anomalous increase in electrical resistivity in the films is in accordance with the two-band model. However, the energy interval between the bands depending on the crystallographic c/a ratio leads to a change in electrical resistivity as a function of temperature.     

Thermal studies of furosemide–caffeine binary system that forms a cocrystal

Thermal techniques, differential scanning calorimetry (DSC), and hot stage microscopy (HSM) have been used to study the interactions between furosemide and caffeine that are known to form a 1:1 cocrystal. This system has been used as an example to study the probable mechanism of cocrystal formation when the individual components, which are polymorphic, are heated. The study indicates that the phase transition of the low temperature stable polymorph of furosemide initiates cocrystal formation. This result suggests increased mass transfer rate can trigger cocrystal formation. The binary phase diagram (composition–temperature plots) of furosemide–cocrystal–caffeine system was determined from the DSC curves. The results imply that the cocrystal forms eutectic with caffeine but not with furosemide. This study has thus exemplified the use of DSC in understanding binary phase system where the two components form a cocrystal.     

Highly Luminescent Colloidal Eu3+‐Doped KZnF3 Nanoparticles for the Selective and Sensitive Detection of CuII Ions

This article describes a green synthetic approach to prepare water dispersible perovskite‐type Eu³⁺‐doped KZnF₃ nanoparticles, carried out using environmentally friendly microwave irradiation at low temperature (85 °C) with water as a solvent. Incorporation of Eu³⁺ ions into the KZnF₃ matrix is confirmed by strong red emission upon ultraviolet (UV) excitation of the nanoparticles. The nanoparticles are coated with poly(acrylic acid) (PAA), which enhances the dispersibility of the nanoparticles in hydrophilic solvents. The strong red emission from Eu³⁺ ions is selectively quenched upon addition of Cu^II ions, thus making the nanoparticles a potential Cu^II sensing material. This sensing ability is highly reversible by the addition of ethylenediaminetetraacetic acid (EDTA), with recovery of almost 90 % of the luminescence. If the nanoparticles are strongly attached to a positively charged surface, dipping the surface in a Cu^II solution leads to the quenching of Eu³⁺ luminescence, which can be recovered after dipping in an EDTA solution. This process can be repeated for more than five cycles with only a slight decrease in the sensing ability. In addition to sensing, the strong luminescence from Eu³⁺‐doped KZnF₃ nanoparticles could be used as a tool for bioimaging.