Synthesis,X-Ray Structure and Characterization of a Triruthenium Cluster Complex Ru_3~Ⅲ(μ_3-O)(μ-CH_3COO)_6(py)_2Cl with Four Steps One-electron Redox Processes

Great attention is currently paid to the synthesis of polynuclear transition metal complexes as well as their photochemical, photophysical, and electrochemical properties. The design of multicomponent systems capable of performing useful light- and/or redox-induced function is of special interest1. The oxo-centered carboxylate-bridge trinuclear ruthenium clusters have been investigated extensively during recent decades because they have remarkable electron-transfer properties, intense visibl…     

On the dynamic electromechanical loading of dielectric elastomer membranes

Dielectric elastomer actuators (DEAs) have received considerable attention recently due to large voltage-induced strains, which can be over 100%. Previously, a large deformation quasi-static model that describes the out-of-plane deformations of clamped diaphragms was derived. The numerical model results compare well with quasi-static experimental results for the same configuration. With relevance to dynamic applications, the time-varying response of initially planar dielectric elastomer membranes configured for out-of-plane deformations has not been reported until now. In this paper, an experimental investigation and analysis of the dynamic response of a dielectric elastomer membrane is reported. The experiments were conducted with prestretched DEAs fabricated from 0.5 mm thick polyacrylate films and carbon grease electrodes. The experiments covered the electromechanical spectrum by investigating membrane response due to (i) a time-varying voltage input and (ii) a time-varying pressure input, resulting in a combined electromechanical loading state in both cases. For the time-varying voltage experiments, the membrane had a prestretch of three and was passively inflated to various predetermined states, and then actuated. The pole strains incurred during the inflation were as high as 25.6%, corresponding to slightly less than a hemispherical state. On actuation, the membrane would inflate further, causing a maximum additional strain of 9.5%. For the time-varying pressure experiments, the prestretched membrane was inflated and deflated mechanically while a constant voltage was applied. The membrane was cycled between various predetermined inflation states, the largest of which was nearly hemispherical, which with an applied constant voltage of 3 kV corresponded to a maximum polar strain of 28%. The results from these experiments reveal that the response of the membrane is a departure from the classical dynamic response of continuum membrane structures. The dynamic response of the membrane is that of a damped system with specific deformation shapes reminiscent of the classical membrane mode shapes but without same-phase oscillation, that is to say all parts of the system do not pass through the equilibrium configuration at the same time. Of particular interest is the ability to excite these deformations through a varying electrical load at constant mechanical pressure.     

Synthesis and characterization of wholly aromatic poly(azomethine)s containing donor–acceptor triphenylamine moieties

N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine was synthesized from N‐(4‐nitrophenyl)‐diphenylamine by the Vilsmeier‐Haack reaction. Soluble aromatic poly(azomethine)s (PAMs) were prepared by the solution polycondensation of N‐(4‐nitrophenyl)‐4′,4″‐bisformyl‐diphenylamine and aromatic diamine in N‐methyl‐2‐pyrrolidone (NMP) at room temperature under reduced pressure. All the PAMs are highly soluble in various organic solvents, such as N,N‐dimethylacetamide (DMAc), chloroform (CHCl₃), and tetrahydrofuran (THF). Differential scanning calorimetry (DSC) indicated that these PAMs had glass‐transition temperatures (T_gs) in the range of 170–230 °C, and a 10% weight‐loss temperatures in excess of 490 °C with char yield at 800 °C in nitrogen higher than 60%. These PAMs in NMP solution showed UV‐Vis charge‐transfer (CT) absorption at 405–421 nm and photoluminescence peaks around 462–466 nm with fluorescence quantum efficiency (Φ_F) 0.10–0.99%. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of these PAMs can be determined from cyclic voltammograms as 4.86–5.43 and 3.31–3.34 eV, respectively. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4921–4932, 2007     

Weak noncovalent Si···F?C interactions stabilized fluoroalkylated rod-like polysilanes as ultrasensitive chemosensors

Noncovalent interactions, such as hydrogen bonding, metal coordination, and π-π stacking, are increasingly being utilized to develop well-ordered and self-organized supramolecular materials. Recently, new types of nonclassical weak interactions, such as C H···π, C H···F C, and C H···O, have been exploited in stabilizing the specific conformations of molecules and molecular assemblies in the solid state. These noncovalent interactions play an important role in materials comprised of polymer chains, because cooperative effects from a large number of weak interactions can lead to drastic changes in its conformation, several properties, and functionalities. The programmed design of synthetic helical polymer with well-defined molecular conformation has been the main subject in modern polymer science and engineering. Silicon-catenated polysilane is an ideal helical silicon quantum wire and polymers with unique photophysical properties. The present review highlights the spectroscopic evidences for through-space weak Si···F C interaction in poly(methyl-3,3,3-trifluoropropylsilane) ( 1 ) in noncoordinating and coordinating solvents by means of NMR (²⁹Si and ¹⁹F) and IR spectroscopies, and viscometric measurement. It was found that 1 is applicable for chemosensors with an extremely high sensitivity and selectivity toward fluoride ions in tetrahydrofuran (THF) and with high sensitivity for nitroaromatic compounds, detected by a decrease in the photoluminescence intensity in THF and in thin solid film. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 5060–5075, 2006     

Synthesis and properties of noncoplanar rigid‐rod aromatic polyhydrazides and poly(1,3,4‐oxadiazole)s containing phenyl or naphthyl substituents

Two new phenyl‐ and naphthyl‐substituted rigid‐rod aromatic dicarboxylic acid monomers, 2,2′‐diphenylbiphenyl‐4,4′‐dicarboxylic acid ( 4 ) and 2,2′‐di(1‐naphthyl)biphenyl‐4,4′‐dicarboxylic acid ( 5 ), were synthesized by the Suzuki coupling reaction of 2,2′‐diiodobiphenyl‐4,4′‐dicarboxylic acid dimethyl ester with benzeneboronic acid and naphthaleneboronic acid, respectively, followed by alkaline hydrolysis of the ester groups. Four new polyhydrazides were prepared from the dicarboxylic acids 4 and 5 with terephthalic dihydrazide (TPH) and isophthalic dihydrazide (IPH), respectively, via the Yamazaki phosphorylation reaction. These polyhydrazides were amorphous and readily soluble in many organic solvents. Differential scanning calorimetry (DSC) indicated that these hydrazide polymers had glass transition temperatures in the range of 187–234 °C and could be thermally cyclodehydrated into the corresponding oxadiazole polymers in the range of 300–400 °C. The resulting poly(1,3,4‐oxadiazole)s exhibited T_g's in the range of 252–283 °C, 10% weight‐loss temperature in excess of 470 °C, and char yield at 800 °C in nitrogen higher than 54%. These organo‐soluble polyhydrazides and poly(1,3,4‐oxadiazole)s exhibited UV–Vis absorption maximum at 262–296 and 264–342 nm in NMP solution, and their photoluminescence spectra showed maximum bands around 414–445 and 404–453 nm, respectively, with quantum yield up to 38%. The electron‐transporting properties were examined by electrochemical methods. Cyclic voltammograms of the poly(1,3,4‐oxadiazole) films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited reversible reduction redox with E_onset at ?1.37 to ?1.57 V versus Ag/AgCl in dry N,N‐dimethylformamide solution. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 6466–6483, 2006     

Polymer electrolyte membranes for the direct methanol fuel cell: A review

The direct methanol fuel cell (DMFC) has the potential to replace lithium‐ion rechargeable batteries in portable electronic devices, but currently experiences significant power density and efficiency losses due to high methanol crossover through polymer electrolyte membranes (PEMs). Numerous publications document the synthesis and characterization of new PEMs for the DMFC. This article reviews this research, transport phenomena in PEMs, and experimental techniques used to evaluate new PEMs for the DMFC. Although many PEMs do not show significant improvements over Nafion®, the benchmark PEM in DMFCs, experimental results show that several new PEMs exhibit lower methanol crossover at similar proton conductivities and/or higher DMFC power densities. These results and recommendations for future research are discussed. © 2006 Wiley Periodicals, Inc. J Polym Sci Parts B: Polym Phys 44: 2201–2225, 2006     

Growth of oxide thin films for optical gas sensor applications

Tungsten trioxide and titanium dioxide thin films were synthesised by pulsed laser deposition. We used for irradiations of oxide targets an UV KrF* (λ = 248 nm, τ_FWHM ≅ 20 ns, ν = 2 Hz) excimer laser source, at 2 J/cm² incident fluence value. The experiments were performed in low oxygen pressure. The (0 0 1) SiO₂ substrates were heated during the thin film deposition process at temperature values within the 300-500 °C range. The structure and crystalline status of the obtained oxide thin films were investigated by high resolution transmission electron microscopy. Our analyses show that the films are composed by nanoparticles with average diameters from a few to a few tens of nm. Moreover, the films deposited at substrate temperatures higher than 300 °C are crystalline. The tungsten trioxide films consist of a mixture of triclinic and monoclinic phases, while the titanium dioxide films structure corresponds to the tetragonal anatase phase. The oxide films average transmittance in the visible-infrared spectral range is higher than 80%, which makes them suitable for sensor applications.     

The Electrochemical Investigation of MEH-PPV in Ionic Liquid

Ionic liquids are a new kind of room-temperature molten organic salts. It can be used as solvents in the organic/polymeric syntheses, and some of them are called "green" solvents because of its recyclability1. Ionic liquids possess the superior properties, such as thermal stability up to 200(C, involatility and re-designability(for both cation and anion). The ionic liquid employed in this work is [bmim] [PF6]- ( butylmethylimidazolium hexafluorophosphate ) which is immiscible with water and h…     

Synthesis and structural characterization of 3-thienyl alkyl imides

Five new thiophene imides having the structures C₄H₃SC(O)N(H)C(O)R (where R=Me, Et, Pr, t-Bu, 1-4) and C₄H₃SCH₂C(O)N(H)C(O)CH₃5 have been prepared. Control over the orientation of the carbonyl groups was achieved by the introduction of a bulky group in the terminal position of the side chain, and molecular modeling calculations indicated that the energy difference between the ct and tt conformations is small. The acidity of 1-4 decreases from Me to t-Bu, and, although 1-4 will not undergo oxidative polymerization, the introduction of a single spacer CH₂ group allows 5 to polymerize.