Effect of radiation dose on the properties of natural rubber nanocomposite

Effect of radiation dose and carbon nanotubes (CNT) on the mechanical properties of standard Malaysian rubber (SMR) was investigated in this study. SMR nanocomposites containing 1–7 phr CNT were prepared using the solvent casting method and the nanocomposites were radiated at doses of 50–200 kGy. The change in mechanical properties, especially, tensile strength (Ts), elongation at break (Eb), hardness and tensile modulus at 100% elongation (M₁₀₀) were studied as a function of radiation dose. The structure and morphology of reinforced natural rubber was investigated by FESEM, TEM and AFM in order to gain further evidence on the radiation-induced crosslinking. It was found that the Ts, M₁₀₀ and the hardness of the SMR/CNT nanocomposites significantly increased with radiation dose; the elongation at break exhibited an increase up to 100 kGy, and a downward trend thereafter. Results on gel fraction further confirmed the crosslinking of SMR/CNT nanocomposites upon radiation.     

Synthesis,physico-chemical and spectral investigations of novel homo-bimetallic mixed-ligand complexes: 57Fe Mössbauer parameters of [Fe2(imda)2(H2O)3Cl]

The newly prepared homo-bimetallic complexes [M₂(imda)₂(H₂O)₄], [M₂(imda)₂(Bipy)₂] (M = Co, Ni or Cu) and [Fe₂(imda)₂(H₂O)₃Cl] (H₂imda = iminodiacetic acid and Bipy = 2,2′-bipyridine) have been studied employing IR, FAB-mass, ¹H and ¹³C NMR, EPR and ligand field spectra, which indicated a high-spin state of metal ion with hexa-coordinate environment. ⁵⁷Fe Mössbauer data of the homo-bimetallic complex [Fe₂(imda)₂(H₂O)₃Cl] confirm a high-spin configuration with Fe (±3/2 → 1/2) nuclear transitions and the presence of Kramer's double degeneracy. At RT, the spin–spin interactions of the neighbouring nuclei (Fe³⁺–Fe³⁺ = S_5/2–S_5/2) are anti-ferromagnetically coupled. However, at LNT, the complex acquires a mixed-valent [Fe^III–Fe^II] composition corroborated from the X-band EPR data. CV studies indicated the presence of quasi-reversible redox Cu^II/I, Cu^II/III, Fe^III/II, Fe^III/I and Fe^II/I couples.     

Molecularly Imprinted Nanospheres by Nonaqueous Emulsion Polymerization

The preparation of nanosized, molecularly imprinted polymer particles by nonaqueous emulsion polymerization is presented. Monodisperse cross‐linked polymer nanospheres with a diameter of around 100 nm were synthesized using a standard monomer mixture of methacrylic acid and ethylene dimethacrylate, containing (±)‐propranolol as a template. The rebinding efficiency of the resulting particles was determined by batch rebinding tests and isothermal titration calorimetry (ITC). The results indicate that the proposed imprinting process under nonaqueous conditions lead to particles with an enhanced capacity of template rebinding compared to both nonimprinted ones and to particles obtained by more conventional emulsion polymerization in water.

     

Spectral and physico-chemical investigations of novel homo-dinuclear di-μ2-alkoxo bridged Schiff base complexes: 57Fe Mössbauer parameters of the Fe(III) complex

Spectral and molecular model computations on homo-dinuclear complexes [M₂L₂(H₂O)₂Cl₂] [L = 1-(salicylaldeneamino)-3-hydroxypropane, M = Cr³⁺, Mn³⁺, Fe³⁺, Co³⁺, Ni³⁺ or Cu³⁺] are consistent with a distorted hexa-coordinate geometry. X-band EPR spectral data indicated a rhombic distortion around Cu(II) ion. Magnetic moment and ⁵⁷Fe Mössbauer data confirmed a high-spin state electronic configuration (t_2g³e_g², S = 5/2) and asymmetric ligand environment around Fe(III) with nuclear transitions Fe(±3/2 → 1/2) exhibiting Kramer's double degeneracy. The neighboring Fe(III) nuclei in the homo-dinuclear species are antiferromagnetically coupled.     

Genotypic Variability Among Soybean Genotypes Under NaCl Stress and Proteome Analysis of Salt-Tolerant Genotype

The present investigation was conducted to evaluate salt tolerance in ten genotypes of soybean (Glycine max L.). Twelve-day-old seedlings, grown hydroponically, were treated with 0, 25, 50, 75, 100, 125 and 150?mM NaCl for 10?days. Growth, lipid peroxidation and antioxidant enzyme activities were evaluated. Growth, measured in terms of length, fresh weight and dry weight of plants, was drastically reduced in Pusa-24 while there was little effect of NaCl treatment on Pusa-37 genotype of soybean. High level of lipid peroxidation was observed in Pusa-24 as indicated by increased level of malondialdehyde. Activities of superoxide dismutase, catalase, ascorbate peroxidase and glutathione reductase were maximum in Pusa-37 where 9-, 1-, 5- and 6-fold increase over control were observed, respectively. The results suggested that Pusa-24 and Pusa-37 are salt-sensitive and salt-tolerant genotype of soybean, respectively, and antioxidant defence system is involved in conferring the sensitiveness and tolerance in these genotypes. Salt-tolerant genotype Pusa-37, was further analysed by 2-dimensional gel electrophoresis to analyse the differential expression of proteins at high salt stress. In the present study, 173 protein spots were identified. Of these, 40 proteins were responsive to salinity in that they were either up- or downregulated. This study could help us in identifying the possible regulatory switches (gene/s) controlling novel proteins of the salt-tolerant genotype of the crop plants and their possible role in defence mechanism.     

Kinetics and mechanism of the photolytic CO-substitutions of cyclopentadienyl(dicarbonyl)iron thiocarboxylate complexes,Cp′Fe(CO)2SCOR (Cp′ = C5H5, ButC5H4,1,3-Bu2tC5H3; R = alkyl,aryl)

The kinetics of the photolytic CO-substitution of CpFe(CO)₂SCOR [Cp = C₅H₅, Bu ^t C₅H₄, 1,3-Bu₂ ^t C₅H₃; R = Me, Bu ^t , Ph, 2-(O₂N)C₆H₄, 3-(O₂N)C₆H₄, 4-(O₂N)C₆H₄, 3,5-(O₂N)₂C₆H₃] with PPh₃ were studied in CH₂Cl₂ at 0 °C by i.r. spectroscopy. The reactions yielded exclusively the mono-CO-substituted derivatives, CpFe-(CO)(PPh₃) SCOR, and were found to follow second order kinetics with first order dependence on the concentration of each reactant. The differences in rates are discussed in terms of current knowledge pertaining to such reactions. An associative mechanism is proposed to account for the kinetic data of the reactions described.     

Synthesis, Characterization, and Biological Activity of n-Tributyltin Derivatives of Pharmaceutically Active Carboxylates

Summary.  Tributyltin(IV) derivatives of six different pharmaceutically active carboxylates were synthesized. The complexes were characterized by different analytical techniques (elemental analysis; infrared, NMR, and mass spectroscopy). ¹¹⁹Sn NMR data were also recorded in six different coordinating and non-coordinating solvents. The antibacterial activities of the compounds were tested using ten different bacteria relative to the reference drugs ampicillin and cephalexin. Received September 20, 2001. Accepted (revised) December 6, 2001     

Beta-N-cyanoethyl acyl hydrazide derivatives: a new class of beta-glucuronidase inhibitors

Eight new beta-N-substituted acyl hydrazides along with their corresponding acyl derivatives were synthesized and screened for in vitro beta-glucuronidase inhibition and found to be active against the enzyme. All of these compounds were found to be noncompetitive inhibitors except for N'-(2-cyanoethyl)-4-hydroxy benzohydrazide (10), which was found to be an uncompetitive inhibitor. Structure-activity relationship studies indicated that the benzyloxy group present in compounds 12 and 13 is responsible for the beta-glucuronidase inhibition activity.     

A massively parallel electrochemical approach to the miniaturization of organic micro- and nanostructures on surfaces

This paper describes a simple and convenient strategy for reducing the dimensions of organic micro-and nanostructures on metal surfaces. By varying electrochemical desorption conditions, features patterned by dip-pen nanolithography or micro contact printing and made of linear alkanethiols or selenols can be gradually desorbed in a controlled fashion. The process is referred to as electrochemical whittling because the adsorbate desorption is initiated at the exterior of the feature and moves inward as a function of time. The whittling process and adsorbate desorption were studied as a function of substrate morphology, adsorbate head and tail groups, and electrolyte solvent and salt. Importantly, one can independently address different nanostructures made of different adsorbates and effect their miniaturization based upon ajudicious selection of adsorbate, applied potential, and supporting electrolyte. Some of the physical and chemical origins of these observations have been elucidated.     

Triphenylphosphine oxide–3‐chlorobenzoic acid (1/1)

In the title compound, C₁₈H₁₅OP·C₇H₅ClO₂, the tri­phenyl­phosphine oxide molecule forms a single directed hydrogen bond with the 3‐chloro­benzoic acid molecule, with an O⃛O=P distance of 2.607 (2) Å. The C—Cl and C=O bonds adopt a cisoid conformation in the 3‐chloro­benzoic acid molecule.