On the role of the bridging dicyanamidobenzene ligand in a new binuclear ruthenium complex: [{Ru(tpy)(thd)}2(mu-dicyd)][PF6] with tpy = 2,2':6',2' '-terpyridine and thd = 2,2,6,6-tetramethyl-3,5-heptanedione

The dicyanamidobenzene-bridge diruthenium complex [{Ru(tpy)(thd)}(2)(mu-dicyd)][PF(6)] ([3][PF(6)]) (dicyd = 1,4-dicyanamidobenzene, tpy = 2,2':6',2' '-terpyridine, thd = 2,2,6,6-tetramethyl-3,5-heptanedione) and its mononuclear counterpart [Ru(tpy)(thd)(Ipcyd)] (2) [Ipcyd = 4-iodophenylcyanamide anion (Ipcyd(-))] were synthesized and fully characterized. Cyclic voltammetry of 3 showed the presence of four reversible one-electron redox couples. UV-vis-NIR spectroelectrochemistry and EPR spectroscopy of the electrogenerated paramagnetic intermediates were used to ascertain the oxidation-state distribution. The stable starting dinuclear complex 3(+) is found to be a ligand-centered anion radical as shown by EPR spectroscopy, magnetic susceptibility measurements, and DFT calculations. Oxidation of 3(+) to 3(2+) led to an EPR silent system due to substantial intramolecular antiferromagnetic interaction of the electron spins carried by the low spin ruthenium(III) atom and the bridging anion radical dicyanamido (dicyd(*)(-)), an observation which was supported by UV-vis-NIR, X-ray structure, and DFT calculations. Complex 3(3+) presented an EPR spectra consistent with a total effective spin S = (1)/(2) issued from an antiferromagnetic interaction of electron spins carried by two low spin ruthenium(III) atoms and the bridging anion radical dicyd(*)(-) in accordance with UV-vis-NIR. This study shows that the dicyanamidobenzene bridging ligand has indubitably a noninnocent behavior.     

Synthesis of quantum dot-tagged submicrometer polystyrene particles by miniemulsion polymerization

Submicrometer fluorescent polystyrene (PS) particles have been synthesized via miniemulsion polymerization using CdSe/ZnS core-shell quantum dots (QDs). The influence of QD concentration, QD coating (either trioctylphosphine oxide (TOPO)-coated or vinyl-functionalized), and surfactant concentration on the polymerization kinetics and the photoluminescence properties of the prepared particles has been analyzed. Polymerization kinetics were not altered by the presence of QDs, whatever their surface coating. Latexes exhibited particle sizes ranging from 100 to 350 nm, depending on surfactant concentration, and a narrow particle size distribution was obtained in all cases. The fluorescence signal of the particles increased with the number of incorporated TOPO-coated QDs. The slight red shift of the emission maximum was correlated with phase separation between PS and QDs, which occurred during the polymerization, locating the QDs in the vicinity of the particle/water interface. QD-tagged particles displayed higher fluorescence intensity with TOPO-coated QDs compared to those with the vinyl moiety. The obtained fluorescent particles open up new opportunities for a variety of applications in biotechnology.     

Identification of the elastic properties of an artificial capsule membrane with the compression test: effect of thickness

The mechanical properties of a capsule membrane are evaluated by means of a compression experiment between two parallel plates. Since large deformations of the membrane are involved, the choice of the wall material constitutive law is essential. In this paper, we explore different classical laws to describe the behavior of the membrane and evaluate also the limit of application of the thin shell approximation. A numerical study of the compression process is performed using Abaqus software and an inverse method is used to identify the material constants of the constitutive laws. The comparison between the model predictions and experimental measurements on capsules with serum albumin-alginate membranes, indicates that the thin shell approximation is valid only for thickness to radius ratios up to 5% and that thick membranes obey non linear elastomer type constitutive laws. The Young modulus of the membrane material is found to increase non-linearly with membrane thickness, thus indicating that fabrication of thicker serum albumin-alginate walls results in capsules stiffer than expected.     

A new highly versatile handle for chemistry on a solid support: the pipecolic linker

The versatility of the pipecolic linker (Pip-linker) is illustrated by the synthesis of modified amino acids, C-terminal-modified pseudopeptides, and cyclic peptides, through side-chain anchoring of a lysine residue. Introduction of the first residue was easily accomplished and the Pip-linker revealed to be robust enough to support various chemical modifications.     

Hydromechanical Modelling of Experimentally Compacted Saturated Argillaceous Porous Media

In order to model the experimental compaction of clays as completely as possible, it is necessary to use the hydromechanical coupled three-dimensional theory for saturated porous media. The proposed formulation is based on elastoplasticity, more precisely on modified Cam-clay model. The identification of the parameters of the model is made by special oedometric experiments at steady state. The compaction experiments are simulated with accuracy in transient and steady states and complement those obtained in a recent study based only on steady state.     

Combining Steric and Electrostatic Stabilization Using Hydrophilic MacroRAFT Agents in an Ab Initio Emulsion Polymerization of Styrene

Hydrophilic (co)polymers carrying a thiocarbonyl thio end group such as poly(dimethylaminoethyl methacrylate), poly(ethylene oxide), and poly(ethylene oxide)‐block‐poly(dimethylaminoethyl methacrylate) have been evaluated as precursors of stabilizers in batch ab initio emulsion polymerization of styrene under acidic conditions to form electrosterically stabilized polystyrene latex particles. As a mixture of P(DMAEMA/H⁺Cl⁻)‐RAFT and PEO‐RAFT failed to give satisfactory results, PEO‐RAFT was used as a control agent for the RAFT polymerization of DMAEMA, and the resulting block copolymer was successfully used in ab initio styrene emulsion polymerization.

     

Generalized Solvable Structures and First Integrals for ODEs Admitting an Symmetry Algebra

The notion of solvable structure is generalized in order to exploit the presence of an algebra of symmetries for a kth-order ordinary differential equation with k > 3. In this setting, the knowledge of a generalized solvable structure for allows us to reduce to a family of second-order linear ordinary differential equations depending on k ? 3 parameters. Examples of explicit integration of fourth and fifth order equations are provided in order to illustrate the procedure.     

Surface modification of iron oxide nanoparticles by a phosphate‐based macromonomer and further encapsulation into submicrometer polystyrene particles by miniemulsion polymerization

A new strategy relying on the use of a phosphate‐based macromonomer (PAM200) to modify the surface of iron oxide nanoparticles was developed for the synthesis of submicrometer polystyrene (PS) magnetic particles. First, iron oxide nanoparticles were synthesized using the coprecipitation of ferrous and ferric salts in alkaline medium. Besides the classical oleic acid (OA)/octane‐based ferrofluid, styrene‐based ferrofluids were elaborated with either OA or PAM200 as the stabilizer. In all cases, maghemite (γ‐Fe₂O₃) was clearly identified, with nanoparticles rather spherical in shape but exhibiting broad particle size distribution (PSD). Both OA and PAM200 led to stable maghemite‐based ferrofluids showing superparamagnetic properties. Further use of these ferrofluids in styrene miniemulsion polymerization resulted in inhomogeneous distribution of maghemite among and inside the polymer particles with OA‐based ferrofluids, whereas PAM200/styrene‐based ferrofluids led to magnetic particles with homogeneous distribution of maghemite inside PS particles. Broad PSD and small nonmagnetic particles were however observed. The true mechanisms operating in these systems are still to elucidate, but this study validates PAM200 as an efficient compatibilizing agent between hydrophilic maghemite and hydrophobic PS. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 327–340, 2008