Phosphorus ligands for iron(III)‐mediated ATRP of styrene via generation of activators by monomer addition

Styrene polymerization via generation of activators by monomer addition (GAMA) for atom transfer radical polymerization (ATRP) has been examined extensively with bulk FeX₃ and FeX₂ at 110 °C in conjunction with various phosphorus‐bearing ligands. It was found that GAMA possesses advantages over normal ATRP. Most importantly, narrower polydispersity index (PDI) values were observed from the styrene polymerizations with Fe(III) over those with Fe(II). Every instance of 2‐(diphenylphosphino)‐N,N′‐dimethyl‐[1,1′‐biphenyl]‐2‐amine and 2‐(diphenylphosphino) pyridine with the Fe(III) system were controlled excellently without addition of any radical initiator or reducing agent additives. Initiator type was found to exert a significant factor to influence on the controllability of polymerization. The initiation of 1‐phenylethyl chloride and methyl‐2‐chloropropionate gave rise to formation of polymers with narrow PDI (1.05–1.20), whereas those from 1‐phenylethyl bromide increased to 1.35. The GAMA of bulk styrene exhibited the best performance in terms of both rate and controllability compared with toluene and anisole. Both formation of block copolymer from the macroinitiator and efficient perturbation of polymerization with 2,2,6,6‐tetramethylpiperidine 1‐oxyl provided firm evidence to support the living and radical characteristics for the GAMA of styrene. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 144–151, 2010     

Poly(cyclohexene oxide)/clay nanocomposites by photoinitiated cationic polymerization via activated monomer mechanism

Poly(cyclohexene oxide) (PCHO)/clay nanocomposites were prepared by in situ photoinitiated activated monomer cationic polymerization. The polymerization of cyclohexene oxide through the interlayer galleries of the clay can provide distribution of the clay layers in the polymer matrix homogenously and results in the formation of PCHO/clay nanocomposites. The exfoliated structures were characterized by X‐ray diffraction spectroscopy, thermogravimetric analysis, transmission electron microscopy, and atomic force microscopy. © 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 5328–5335, 2009     

Steps towards a practical synthesis of macrocyclic bisbenzylisoquinolines

There are more than 400‐reported bisbenzylisoquinoline alkaloids, many with interesting biological activity, but the reported syntheses are long and low yielding. As a result, there have been no systematic attempts at exploitation of the potential therapeutic applications. The concept of a sulfur ‘stitch’, restricting the conformational freedom of intermediates in the synthesis, will potentially allow analogues of the natural products to be prepared using relatively efficient routes. The synthesis of intermediate sulfur heterocycles is reported, based on 2,8‐dimethylphenoxathiin, leading via 2,8‐bis(bromomethyl)phenoxathiin‐10,10‐dioxide to a synthesis of 3,4,8,9‐tetrahydro‐13‐oxa‐6‐thia‐2,10‐diazapentacene, a key potential intermediate on the route to a variety of macrocyclic bisbenzylisoquinolines.     

Elastoplastic analysis of nonlinearly hardening variable thickness annular disks under external pressure

Based on von Mises’ yield criterion, deformation theory of plasticity and Swift’s hardening law, elasto-plastic deformation of variable thickness annular disks subjected to external pressure is studied. A nonlinear shooting method using Newton’s iterations with numerically approximated tangent is designed for the solution of the problem. Considering a thickness profile in the form of a general parabolic function, the condition of occurrence of plastic deformation at the inner and outer edges of the annular disk is investigated. A critical disk profile is determined and the corresponding elastic–plastic stresses as well as the residual stress distribution upon removal of the applied pressure are computed and discussed.     

Printable Bioelectronics To Investigate Functional Biological Interfaces

Thin‐film transistors can be used as high‐performance bioelectronic devices to accomplish tasks such as sensing or controlling the release of biological species as well as transducing the electrical activity of cells or even organs, such as the brain. Organic, graphene, or zinc oxide are used as convenient printable semiconducting layers and can lead to high‐performance low‐cost bioelectronic sensing devices that are potentially very useful for point‐of‐care applications. Among others, electrolyte‐gated transistors are of interest as they can be operated as capacitance‐modulated devices, because of the high capacitance of their charge double layers. Specifically, it is the capacitance of the biolayer, being lowest in a series of capacitors, which controls the output current of the device. Such an occurrence allows for extremely high sensitivity towards very weak interactions. All the aspects governing these processes are reviewed here.     

Thermal and neutron shielding properties of 10B containing UV cured hybrid coatings

¹⁰B containing organic–inorganic hybrid coating material based on a UV-curable formulation was prepared via anhydrous sol–gel technique. UV curable coatings were applied on Plexiglas (PMMA) substrates. The molecular structure of the coating material was analyzed by ATR-FTIR spectroscopy technique. The characterization of the UV-curable coating was evaluated by various techniques such as gel content, abrasion resistance, chemical resistance, pencil hardness, pendulum hardness, MEK rubbing test, contact angle, cross-cut test, gloss, transmittance test, neutron absorption, Limiting Oxygen Index and stress–strain tests. Hybrid coatings showed a significant enhancement in radiation shielding properties. The thermal behavior of coatings was also evaluated. It is observed that the thermal stability of coatings mainly depends on their boron and silicate contents. Results of all analysis conducted on hybrid films, and coatings were discussed.     

Acid-catalyzed reactions of (3-(naphthalen-2-yl)-2,2-bis(trimethylsilyl)oxiran. A new synthesis of functional-group-substituted vinylsilanes

The magnesium bromide-diethyl etherate-catalyzed ring-opening of (3-(naphthalen-2-yl)-2,2-bis(trimethylsilyl)oxiran 2 with thiophenols affords (1-trimethylsilylvinyl)sulfides 3 and the (1-bromovinyl)silane 4. Nucleophilic attack occurs regioselectively at the position α- to silicon. The compound 2 has been converted into the (1-trimethylsilylvinyl)amide 5 with an excess of acetonitrile and into the (1-trimethylsilylvinyl)acetate 6 with acetic acid/acetic anhydride. These reactions proceed with catalytic amounts of boron trifluoride-diethylether. Treatment of 2 with acetic acid alone gives naphthaldehyde. The epoxide 2 reacts also with MgBr₂·OEt₂, MeLi/CuI, HX (XBr or Cl) and LiAlH₄ with nucleophilic attack at the bis(trimethylsilyl)-substituted carbon.     

New antidepressant drug candidate: Hypericum montbretti extract

This study was designed to investigate possible antidepressant-like effects of the extract prepared from the flowers of Hypericum montbretti Spach. (Guttiferae, Clusiaceae). Phytochemical constituents of the methanolic extract were analysed by HPLC method. The main flavonoid component was detected as rutin, and another highly concentrated phenolic compound was quercitrin. Antidepressant activity of the extract was examined by tail suspension and modified forced swimming tests, whereas the motor coordination of the animals was tested by the Rota-Rod apparatus. Reboxetine at a dose of 20 mg?kg?1 was used as a reference drug. Dose-dependent antidepressant activity was observed in both tests following the administration of extract at 100 and 250 mg?kg?1 doses. To the best of our knowledge, this is the first study reporting the antidepressant activity of H. montbretti extract. Additionally, the results of this work support previous papers reporting the antidepressant activity of rutin.