Electroinitiated Polymerization of N-Vinylcarbazole by Direct Electron Transfer

Electroinitiated polymerization of N-vinylcarbazole has been accomplished by constant potential electrolysis. It was found that direct electron transfer from the monomer to the anode initiates the polymerization even at a potential as low as +0.95 V versus Ag^?/ Ag⁺. Dichloromethane was used as the solvent, and the electrolyte was tetrabutylammonium fluoroborate. Conversions as high as 86% were reached even when a microelectrode was used. Effects of electrode area, temperature, and electrode potential on polymerization were studied. Percent conversion was followed by cyclic voltammetry.     

Access to New Endoperoxide Derivatives by Electrochemical Oxidation of Substituted 3‐Azabicyclo[4.1.0]hept‐4‐enes

A series of substituted 3‐azabicyclo[4.1.0]hept‐4‐ene derivatives were prepared and analysed by cyclic voltammetry. Preparative aerobic electrochemical oxidation reactions were then carried out. Three original endoperoxides were isolated, characterised and subjected to antimalarial and cytotoxicity activity assays.     

Highly efficient metal‐free organic catalysts to design new Environmentally‐friendly starch‐based blends

A one‐step process is reported to directly synthesize blends of poly(trimethylene carbonate) (PTMC) with a modified granular starch. Trimethylene Carbonate (TMC) ring‐opening polymerization is performed in the presence of native starch particles in bulk conditions at 150 °C and the efficiency of metal‐free organic catalysts (TBD and phosphazene superbases P1‐t‐Oct, P2‐t‐bu, and P4‐t‐bu) are investigated to replace the organo‐metallic stannous octanoate initiator. TMC monomer is successively converted into PTMC and the robustness of organic catalysts is highlighted with significant activities at very low concentrations (<100 ppm), where stannous octanoate is inefficient. Reactivity of starch toward TMC ROP is deeply investigated by NMR techniques and a starch‐graft‐PTMC is indirectly evidenced. Starch substitution degree reaches 0.9% indicating that PTMC grafting only occurs at the surface of swollen granular starch. PTMC graft length from the starch surface remained low in the range 2–12 and model ROP reactions highlight the role of TMC hydrolysis on PTMC graft length. Despite low PTMC grafts, a fine dispersion of intact starch particles into the PTMC matrix is evidenced. Consequently, metal‐free organic catalysts at low concentrations are promising candidates for synthesizing blends of PTMC with high loadings of surface‐modified starch (32% by weight) in 2 min within a one‐step process. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 493–503     

Purification of a 166mHo solution by successive high-performance liquid chromatography and gravitational chromatography for half-life determination

A methodology to purify a ^166mHo solution has been developed by a combination of activity and mass concentration measurements in order to further determine the ^166mHo half-life. The isobaric interference at m/q ? 166 requires Ho purification from non-natural Er with a high purification degree due to the large amount of Ho as opposed to Er. The Ho/Er separation was achieved using high-performance liquid chromatography on a semi-preparative column followed by purification on gravitational chromatography. The efficiency of the separation was evaluated after precise determination of the Er isotopic composition. The purification methodology enabled to separate Ho from Er.     

Biobased vinyl levulinate as styrene replacement for unsaturated polyester resins

Vinyl levulinate (VL) is used as a biobased reactive diluent in styrene (St)‐free unsaturated polyester resins (UPR). The reactivity ratios for the radical copolymerization of VL with diethyl fumarate (DEF) are determined by the Jaacks method (r_VL = 0.01 and r_DEF = 0.81 at 60 °C in DMSO‐d₆). The properties of UPRs having a stoichiometric ratio between unsaturated groups from the UPR and either St or VL are compared. Defect‐free, slightly yellow, transparent, and rigid thermosets are obtained after a mild curing cycle. Due to unfavorable reactivity ratios about 5.5 wt % of unpolymerized VL remains inside the network and acts as plasticizer. Consequently, compared with St‐based ones, VL‐based UPRs exhibit lower α relaxation (T_α = 180 and 100 °C, respectively), lower elastic moduli at the rubbery plateau (G′ = 10⁸ and 10⁷ Pa) and lower mechanical properties as measured by three points bending tests. Strain at break (ε_f = 1.8 ± 0.2%) and Charpy impact strength (～2.7 ± 0.3 kJ m^?2) are comparable independently of the RD chemical nature. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3356–3364     

Carbon Nanotubes/Heteroatom‐Doped Carbon Core–Sheath Nanostructures as Highly Active,Metal‐Free Oxygen Reduction Electrocatalysts for Alkaline Fuel Cells

A facile, scalable route to new nanocomposites that are based on carbon nanotubes/heteroatom‐doped carbon (CNT/HDC) core–sheath nanostructures is reported. These nanostructures were prepared by the adsorption of heteroatom‐containing ionic liquids on the walls of CNTs, followed by carbonization. The design of the CNT/HDC composite allows for combining the electrical conductivity of the CNTs with the catalytic activity of the heteroatom‐containing HDC sheath layers. The CNT/HDC nanostructures are highly active electrocatalysts for the oxygen reduction reaction and displayed one of the best performances among heteroatom‐doped nanocarbon catalysts in terms of half‐wave potential and kinetic current density. The four‐electron selectivity and the exchange current density of the CNT/HDC nanostructures are comparable with those of a Pt/C catalyst, and the CNT/HDC composites were superior to Pt/C in terms of long‐term durability and poison tolerance. Furthermore, an alkaline fuel cell that employs a CNT/HDC nanostructure as the cathode catalyst shows very high current and power densities, which sheds light on the practical applicability of these new nanocomposites.     

Preparation of Chiral Amino Esters by Asymmetric Phase‐Transfer Catalyzed Alkylations of Schiff Bases in a Ball Mill

The asymmetric alkylation of Schiff bases under basic conditions in a ball mill was performed. The starting Schiff bases of glycine were prepared beforehand by milling protected glycine hydrochloride and benzophenone imine, in the absence of solvent. The Schiff base was then reacted with a halogenated derivative in a ball mill in the presence of KOH. By adding a chiral ammonium salt derived from cinchonidine, the reaction proceeded asymmetrically under phase‐transfer catalysis conditions, giving excellent yields and enantiomeric excesses up to 75 %. Because an equimolar amount of starting material was used, purification was greatly simplified.     

An Incompressible Fluid in a Weakly Deformable Shell. Part I: Analysis of the Model

We consider the flow of a viscous incompressible fluid in a pipe when the boundary is a deformable shell of Naghdi type. We prove that the corresponding system of partial differential equations has a solution when the deformation of the shell is smooth and small enough. We propose an algorithm that uncouples the unknowns and prove its convergence.     

Study of the Release Mechanism of Terminalia chebula Extract from Nanoporous Silica Gel

Sol/gel-derived silica gel was prepared at room temperature from tetraethyl orthosilicate precursor. The extracts of Terminalia chebula (Haritoki) were entrapped into the porous silica gel. Fourier transform infrared analysis revealed the proper adsorption of herbal values in the nanopores of the silica gel. Porosity was estimated by transmission electron microscope studies. The release kinetics of the extract in both 0.1 N HCl, pH 1.2, and Phosphate-buffer saline (PBS), pH 7.2, were determined using UV–Vis spectroscopy. Different dissolution models were applied to release data in order to evaluate the release mechanisms and kinetics. Biphasic release patterns were found in every formulation for both the buffer systems. The kinetics followed a zero-order equation for first 4 h and a Higuchi expression in a subsequent timeline in the case of 0.1 N HCl. In the case of PBS, the formulations showed best linearity with a first-order equation followed by Higuchi’s model. The sustained release of the extract predominantly followed diffusion and super case II transport mechanism. The release value was always above the minimum inhibitory concentration.