Photoinitiated alternating copolymerization of vinyl ethers with chlorotrifluoroethylene

The photoinitiated copolymerization of chlorotrifluoroethylene (CTFE) with several vinyl ethers [ethyl vinyl ether (EVE), 2‐chloroethyl vinyl ether (CEVE), cyclohexyl vinyl ether (CHVE), 4‐hydroxybutyl vinyl ether (HBVE)] was studied. CTFE is an acceptor monomer (e ～ 1.5) whereas vinyl ethers are donor monomers (e ～ ?1.5), and therefore their copolymerization led to alternating copolymers, as indicated by elementary analysis. The equilibrium constant (K_F) of the charge‐transfer complex formation (CTC) was determined by ¹⁹F NMR spectroscopy. Under our experimental conditions, K_F was low for CHVE/CTFE and HBVE/CTFE systems, 0.058 and 0.013 l mol^?1 respectively. It can be assumed that the copolymerization involves the free monomers rather than propagation via the donor–acceptor complex. The alternating structure arises from the great difference in polarity between the two types of monomers. Several functional copolymers were prepared in good yield and with molecular weight close to 15 000 g mol^?1. © 2002 Society of Chemical Industry     

Interactions of focal cortical lesions with error processing: Evidence from event-related brain potentials.

Electrophysiological and hemodynamic studies have suggested that structures in the vicinity of the anterior cingulate cortex are involved in performance monitoring, particularly in detection of errors. Bidirectional interactions between the frontomedian system involved in performance monitoring and the lateral prefrontal cortex as well as the orbitofrontal cortex have been proposed, but few studies have directly addressed this issue. The authors used a speeded flankers task to investigate error-related event-related potentials in 3 patient groups with different focal cortical lesions. Whereas bilateral frontopolar lesions involving the orbitofrontal cortex as well as temporal lesions did not alter the error-related negativity (ERN), lesions of the lateral frontal cortex resulted in an abolition of the ERN and in a reduction of the error positivity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

m‐Chloroaniline emulsion polymerization,macromolecular chain structure and electrochemical properties

Poly(m‐chloroaniline) (PmClAn) was synthesized by emulsion polymerization. The influences of reaction temperature and initiator concentration on polymerizations were studied. It was found that PmClAn with number‐average molecular weight of 1.85 × 10³ g mol^?1 was obtained by the following conditions: 80 °C, [monomer] = 0.187 × 10^?3 mol l^?1, [sodium lauryl sulfate] = 4.8 × 10^?2 mol l^?1, [potassium peroxydisulfate] = 5.6 × 10^?2 mol l^?1, reaction period = 2.0 h. ¹H NMR, FTIR, and transmission and scanning microscopy were used for structural characterization of PmClAn. It was shown that the ratio of benzoid to quinoid units in the macromolecular chain was respectively 3:2, and that PmClAn has a typical crystalline monoclinic form. A PmClAn molecular chain configuration was also proposed on the basis of crystallographic data. Cyclic voltammetry experiments revealed the PmClAn membrane electrode electroactivity. This electroactivity increased when the polymer was proton‐doped. When Pt particles were electrodeposited onto the polymer membrane electrode, they presented a preferred orientation. Isopropanol oxidation intensities with platinized PmClAn modified electrodes were larger than with a platinized Pt electrode. We also found that oxidation occurred mainly on the Pt particles deposited on the polymer, and that the anodic peak potential changed with polymer and its doping level. These results indicated that the Pt particles interacted with the polymer and that catalytic properties could be observed. © 2002 Society of Chemical Industry     

A Hermitian finite difference method for the solution of parabolic equations

A high accuracy difference method (hermitian method) for the solution of evolution equations of parabolic type is presented. Its most original feature is to use several unknowns (the value of the solution and its spatial derivatives) at every nodal point of the computational grid. It is shown that this method has better computational performance than classical schemes on non-uniform and coarse meshes.     

Identification of female sex pheromone in alfalfa blotch leafminer,Agromyza frontella (Rondani)(Diptera: Agromyzidae)

Gas chroinatography of hexane extracts of 3-day-old virgin A.frontella adults revealed a branched saturated hydrocarbon present only in females. This compound was isolated by argentation chromotography and preparative GC, identified by GC and GC-MS as 3,7-dimethylnonadecane, and subsequently synthesized. Three-day-old virgin females contained 54.1 ± 3.5 ng (± SEM;N = 48) of 3,7-dimethylnonadecane. Male cadavers do not elicit male courtship behavior, but when treated with 18 ng of 3,7-dimethylnonadecane they were as attractive as cadavers of 3-day-old virgin females. Black cotton knots were less attractive than male cadavers when treated with 3,7-dimethylnonadecane, but all bioassays indicated that this compound is an important semiochemical modulating male mating behavior.     

A low‐energy emulsification batch mixer for concentrated oil‐in‐water emulsions

This work shows the formation of a high internal phase ratio oil‐in‐water (O/W) emulsion using a new type of a two‐rod batch mixer. The mixture components have sharply different viscosities [1/3400 for water‐in‐oil (W/O)], similar densities (1/0.974 for W/O), and an O/W ratio of 91% (wt/wt). The simple design of this mixer leads to a low‐energy process (10⁶ < energy density [J m^?3] < 10⁷), characterized by low rotational speed and laminar flow. The droplet size distribution during the emulsification was investigated according to different physical and formulation parameters such as stirring time (few minutes < t < 1 h), rotational speed (60 < Ω < 120 rpm), surfactant type (Triton X‐405 and X‐100), concentration (from 1 to 15.9 wt % in water), and salt addition (30 g/L). We show that all studied parameters allow a precise control of the droplet size distribution and the rheology. The resulting emulsions are unimodal and the mean droplet diameter is between 30 μm and 8 μm. © 2010 American Institute of Chemical Engineers AIChE J, 2011     

Two-dimensional nanometric confinement of entangled polymer melts

We present a Monte Carlo study of the structure of an entangled polymer melt confined between parallel plates separated by a distance smaller than the radius of gyration R_g of the chains. Within that regime, we find a dramatic increase in the molecular weight between entanglements and in the eigenvalues of the gyration tensor of the chains in the plane of the plates. The chains however appear to retain their Gaussian behavior throughout confinement. Interestingly, we also observe that individual chains at short length scales form “globules” whose density and size increase with the extent of confinement.     

Methane Steam Reforming in Microchannel Reactors: Technical Challenges and Performances Benefits

The steam reforming of methane was studied over microstructured platelets coated with catalysts and assembled as microreactors. Three different bonding procedures have been applied to assemble the microchannel platelets. The effect of the assembly procedure on the catalytic performance has been investigated for both nickel and rhodium based catalysts. The brazing technology leads, contrary to laser welding, to fully connected platelets resulting in a superior catalytic activity due to better heat transfer and gas flow distribution. Outstanding performances in term on hydrogen productivity and catalytic stability are obtained on the low temperature brazed system washcoated with a Rh-alumina catalyst.     

Poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) and Poly(propylene carbonate) Blends: an Efficient Method to Finely Adjust Properties of Functional Materials

Polyhydroxyalkanoate (PHA) and poly(propylene carbonate) (PPC) are blended in order to investigate their mutual contributions in terms of functional properties. A wide range of blend composition is processed through extrusion from dry blends. Droplet‐matrix morphology is observed for all samples. Thermal investigations reveal the PPC effect on the PHA crystallization process with a decrease and broadening of the crystallization temperature window and on the depression of its glass transition temperature. This investigation also confirms the as yet un‐reported non‐miscibility of this kind of blend. However, a slight phase interaction is expected since thermal behavior of PHA is impacted. The fragile behavior of PHA is balanced by the high ductility of PPC. The weak strain at break of PHA can thus be increased by up to 200% although a significant amount of PPC is needed to start modifying this property. Stress at break and modulus are linearly decreased from pure PHA to pure PPC values. PPC also acts as an impact modifier for PHA. In terms of barrier properties, PHA brings a large contribution even at low content to the initially high oxygen and water vapor permeability of PPC.