Nanoscale highly filled epoxy nanocomposite

A new technique has been developed to prepare a highly filled epoxy-montmorillonite (MMT) nanocomposite using an organically modified MMT. Composites with clay content up to 70 wt.% exhibit unusual transparency, which is related to the spatial distribution of the mineral nanodomains. Dispersion of the layered silicate within the crosslinked epoxy matrix was verified using X-ray diffraction pattern, revealing layer spacings of 30 and 70 Å. Examination of these materials by scanning electron microscopy and transmission electron microscopy showed that intercalates have wholly layered morphology at all scales, oriented parallel to the surface of the specimen and have good wetting to the silicate surface by the epoxy matrix. Silicate lamellae intercalated with epoxy resin assembled into a cluster of about 50-120 nm thickness. These clusters assembled into superclusters with an average thickness of 300 nm. Studies by the Vickers hardness test of an epoxy-MMT nanocomposite containing 60 wt.% MMT indicated that the diamond pyramid hardness was 10-29 kg/mm².     

Aldehyde detection by chromogenic/fluorogenic oxime bond fragmentation

Amination of 4-nitrophenol, umbelliferone and 4-methylumbelliferone gave the corresponding oxyamines 1-3. These oxyamines react with aldehydes and ketones to form oximes. In the case of aliphatic aldehydes and electron-poor aromatic aldehydes, the oximes undergo base-catalyzed fragmentation in aqueous buffer in the presence of bovine serum albumin to give the parent phenols, which is the acyclic analog of Kemp's elimination reaction of 5-nitrobenzisoxazole 28. The process can be used as a spectrophotometric assay for formaldehyde under aqueous neutral conditions.     

A hybrid nanofluid analysis near a parabolic stretched surface

Two dimensional incompressible steady viscous nano-fluid flow with the impacts of heat generation and porous medium is examined numerically. For this objective Ti₆Al₄v are taken as nano-particles dispersed in different base fluids such as methanol, engine oil and water. Basically in this study we will compare three different nano-fluids to assess their flow behaviour and thermal performance. The flow model is developed under certain assumptions. The two dimensional non-linear PDEs are converted into non-linear ODEs with suitable transformation. The numerical procedure is adopted to find the results by using Bvp4c technique in MATLAB. Moreover, graphs are generated for various parameters against the temperature and velocity profiles. The fluid behaviour for different parameter is examined on velocity and temperature profile. It is depicted that for high values of volume fraction and curvature parameter nano-particles leads to high velocity and temperature profile. Moreover, velocity profile decreases for permeability parameter, while temperature profile enhances for heat generation parameter. The influence of Nusselt number and skin friction also assessed. The model of entropy generation is also presented.     

Preparation,morphology and electrical conductivity of polyaniline/polyoxyalkylene–montmorillonite exfoliated nanocomposites

Polyaniline (PANI)/organoclay exfoliated nanocomposites containing different organoclay contents (14–50 wt%) were prepared. PANI emeraldine base (EB) and oligomeric PANI (o‐PANI) were intercalated into montmorillonite (MMT) modified by four types of polyoxyalkylene diamine or triamine (organoclay) using N‐methyl pyrolidinone (NMP) as a solvent in the presence of 0.1 M HCl. o‐PANI and EB have been synthesized by oxidative polymerization of aniline using ammonium peroxydisulfate (APS). Infrared absorption spectra (IR) confirm the electrostatic interaction between negatively charged surface of MMT and positively charged sites in PANI. X‐ray diffraction (XRD) studies disclosed that the d₀₀₁ spacing between interlamellar surface disappeared at low content of the organoclay. The morphology of these materials was examined by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Electrical conductivities of the PANI‐organoclay and o‐PANI‐organoclay nanocomposites were 1.5 × 10^?3–2 × 10^?4 and 9.5 × 10^?7–1.8 × 10^?9 S/cm, respectively depending on the ratio of PANI. Copyright © 2007 John Wiley & Sons, Ltd.     

Antimicrobial and antitumor activities of 1,2,4‐triazoles/polypyrrole chitosan core shell nanoparticles

Combination of natural biodegradable polymer with a synthetic polymer offers excellent properties for the support in drug delivery system. For this purpose, biodegradable conductive nanoparticle polypyrrole based on chitosan (PPC) has been prepared via oxidative polymerization of pyrrole in presence of chitosan using FeCl₃ as oxidant in acidic medium and used as a carrier for 1,2,4‐triazoles. The resultant nanoparticles were characterized by X‐ray diffraction, Fourier transform infrared analysis, transmission electron microscopy, scanning electron microscopy, and thermal gravimetric analysis. The results indicate that spherical nanoparticle of average diameter 52 ± 8 nm was successfully prepared. The spherical particles were composed of dark sphere surrounded by grey shell. A circumferential dark ring is observed in the shell after loading 1,2,4‐triazoles into PPC nanoparticles. The loaded triazoles were released almost linearly against time in a sustained fashion into different pH media. The mechanism of triazoles release was determined using different kinetics equations. The antibacterial activities against the gram‐negative and gram‐positive bacteria were examined. Furthermore, the antitumor activity of PPC nanoparticles loaded 1,2,4‐triazoles was also examined against Ehrlich ascites carcinoma cells and breast cancer cell line (MCF7). Polypyrrole chitosan loaded nanoparticles exhibited higher antitumor activity than 1,2,4‐triazoles.     

A Novel,Chemoselective and Efficient Production of Amines from Azides Using ZrCl4/NaBH4

A practical & cheaper reagent system ZrCl₄/NaBH₄ is used for the production of amines from azldes is described.     

Effect of ionic temperature on the modulational instability of ion acoustic waves in the presence of a magnetic field

The modulational instability of ion acoustic waves is studied in the presence of a dc magnetic field, taking the ion temperature into account. It is well known that the instability sets in for wave numbers exceeding 1.47 k_D when there is no magnetic field and the ion temperature is negligible. The instability behaviour, however, changes drastically when either the magnetic field is switched on or the ion temperature becomes important or both. In general three different regions emerge wherein the waves becomes modulationally unstable. The relative sizes of these regions change as the magnetic field, the angle of propagation and the ion temperature are varied.     

Ion acoustic soliton propagation in a magnetized relativistic plasma

Summary The Korteweg-de Vries equation for ion acoustic waves in the presence of weakly relativistic ion streaming velocity is derived in a magnetic plasma. It is found that relativistic effects are important in the solitary wave propagation for both fast and slow modes. Earlier results are reconfirmed. To speed up publication, the authors of this paper have agreed to not receive the proofs for correction.     

Living ring-opening metathesis polymerization of norbornenes bay-functionalized perylene diimides

Ring-opening metathesis polymerization (ROMP)-derived poly(oxanorbornene imide)s bearing bay-linked mono - alkoxy -M1 and 1,7-di-alkoxy M2 functionalized perylene diimides (PDIs) were synthesized using Grubb's third ( G3 ) and Hoveyda-Grubbs second generation ( HG2 ) ruthenium-alkylidene metathesis initiators. The mono-alkoxy-derived PDI-based non-ladderphane polymer poly M1 displayed 67% to 77% of the trans olefin content in the polymer chain depending on the initiator used for the polymerization. When using the symmetrical 1,7-di-alkoxy-derived PDI-based polymer poly M2 having the ladderphane type-structure, this displayed a significant amount of cis and trans olefin contents in the polymer chains, irrespective of the type of initiators used for the polymerization. ROMP of both monomers M1 and M2 proceeded in a well-controlled manner with a linear dependence of molecular weight on the monomer/initiator ratio using G3 as initiator. Optical properties of the ladderphane-based poly M2 and non-ladderphane-based poly M1 were characterized in both solution and the film state. X-ray diffraction (XRD) analysis for all the polymers showed significant π-stacking in the thin film state with ordered molecular packing and closer values of d-spacing for both poly M1 and poly M2 . Film morphology examined by AFM elucidated homogenous smooth polymer surface for both polymers in general, but with some irregularities observed for poly M1 . In addition, CV analysis revealed both polymers could be good candidates as electron-accepting materials, with excellent film-forming ability, and thermal stability.     

Thiazole fused S,N-heteroacene step-ladder polymeric semiconductors for organic transistors

Ladder-type thiazole-fused S,N-heteroacenes with an extended π-conjugation consisting of six (SN6-Tz) and nine (SN9-Tz) fused aromatic rings have been synthesized and fully characterized. To date, the synthesis of well-defined fused building blocks and polymers of π-conjugated organic compounds based on the thiazole moiety is a considerable synthetic challenge, due to the difficulty in their synthesis. Acceptor–donor building blocks M1 and M2 were successfully polymerized into ladder homopolymers P1–P2 and further copolymerized with a diketopyrrolopyrrole unit to afford step-ladder copolymer P3. The optical, electronic, and thermal properties, in addition to their charge transport behavior in organic thin-film transistors (OTFTs), were investigated. The results showed an interesting effect on the molecular arrangement of the thiazole-based ladder-type heteroacene in the crystal structure revealing skewed π–π-stacking, and expected to possess better p-type semiconducting performance. The polymers all possess good molecular weights and excellent thermal properties. All the polymer-based OTFT devices exhibit annealing temperature dependent performance, and among the polymers P3 exhibits the highest mobility of 0.05 cm² V⁻¹ s⁻¹.

Ladder-type thiazole-fused S,N-heteroacenes with an extended π-conjugation consisting of six (SN6-Tz) and nine (SN9-Tz) fused aromatic rings have been synthesized and fully characterized.