Coordination Patterns of the Diphenyl-Phosphinodithioato Ligand in Tellurium Compounds

Abstract.

Solid state monomeric structures with monometallic biconnective (bidentate) diphenylphosphinodithioato groups were found in Ph₂Te(S₂PPh₂)₂ (1) or [Ph₃Te][S₂PPh₂] (2), while in the polymeric associations [Te₂(S₂PPh₂)₂]_n (3) and [PhTeS(S)PPh₂]_n (4) bimetallic biconnective (bridging) and monodentate biconnective (bridging) patterns were established by X-ray diffractometry. [Te(S₂PPh₂)₃]₂ (5) exhibits an unusual dimeric structure, with both monometallic biconnective and bimetallic triconnective ligand units.     

Synthesis and microbiological evaluation of several benzocaine derivatives

Starting from benzocaine, a well-known anaesthetic, ten derivatives were synthesized and characterized by UV–vis, IR, NMR, and elemental analysis. Most of the compounds contain residues with recognized biological activity, like nicotinic acid (vitamin B3 or PP), biotin (vitamin B7 or H), lipoic acid (thioctic acid), adamantine, as well as other residues of crown-ether type, benzofurazane, naphtylurea, di- and tri-nitrobenzene, and a nitroxide radical. The biological evaluation of the obtained compounds included hydrophobicity (lipophobicity) assay, total antioxidant and microbiological activity tests.     

An Approximate Kinetic Treatment of Slow‐Initiated Living Polymerization. II. First‐Order Initiation and Half‐Order Propagation

An approximate analytical solution of the set of differential equations modeling the anionic polymerization of styrene is presented. By using this solution, a new method for calculating the initiation rate constant for this polymerization process was developed.     

Two phase photochemical synthesis of silver nanoparticles and their impact on the chlorophylls

Abstract

We have designed an experimental study dedicated to silver nanotoxicity using a suspension of citrate-silver nanoparticles, obtained by photochemical reduction. Fine granularity of generally symmetrical shape nanoparticles were evidenced by tansmission electron microscopy. The localized surface plasmon resonance spectral band revealed the intensification of silver nanoparticle formation under UV exposure. The nanotoxicity of silver nanoparticles was tested on cereal sprouts by measuring the concentrations of chlorophylls and carotenes in the green tissue. The differences between control samples, supplied with distilled water and test samples, loaded with different volumes of silver nanoparticles suspension were analyzed statistically, and compared with literature reports.     

Large amplitude oscillatory extension of soft polymeric networks

Using a filament stretching rheometer surrounded by a thermostatic chamber and equipped with a micrometric laser, it is possible to measure large amplitude oscillatory elongation (LAOE) on elastomeric based networks with no base flow as in the LAOE method for polymer melts. Poly(dimethylsiloxane)-based networks, considered as a model system for studying the development of soft elasticity, are mechanically characterised through reversed LAOE deformation, applying oscillatory measurements with several amplitudes and frequencies.     

Simultaneous measurement of mechanical and surface properties in thermoresponsive, anchored hydrogel films

Hydrogel films have been used extensively in the preparation of biosensors and biomedical devices. The characteristics of the aqueous interface of the polymer layer are significant for the biosensor or device function; likewise, the changing mechanical properties of thermoresponsive polymers are an important feature that affects the polymer behavior. Atomic force microscopy was used here to characterize both the surface and the mechanical properties of polymeric hydrogel films prepared from a thermoresponsive terpolymer of N-isopropylacrylamide and acrylic acid with benzophenonemethacrylate as a photoreactive cross-linker comonomer. The force-distance curves thus obtained were analyzed to assess both the surface forces and the mechanical response that were associated with the hydrogel. These properties were investigated as a function of temperature, in water and in Tris buffer, for different degrees of polymer cross-linking. For samples in water, the distance over which the surface forces were effective was found to remain constant as the temperature was increased from 26 to 42 °C, even though the mechanical response indicated that the samples had been heated past the lower critical solution temperature, or LCST. The bulk of the polymer becomes less soluble above the LCST, although this does not seem to affect the surface properties. This may be due to the segregation of the acrylic acid-rich polymer segments near the gel surface, which is in agreement with reports for related systems.