Fatty Acid Methyl Esters as Biosolvents of Epoxy Resins: A Physicochemical Study

The C8 to C18 fatty acid methyl esters (FAME) have been compared as solvents for two epoxy resin pre-polymers, bisphenol A diglycidyl ether (DGEBA) and triglycidyl paminophenol ether (TGPA). It was found that the solubilization limits vary according to the ester and that methyl caprylate is the best solvent of both resins. To explain these solubility performances, physical and chemical properties of FAME were studied, such as the Hansen parameters, viscosity, binary diffusion coefficient and vaporization enthalpy. Determination of the physicochemical parameters of FAME was carried out by laboratory experimentations and by calculation from bibliographic data. The Hansen parameters of FAME and epoxy resins pre-polymers were theoretically and experimentally determined. The FAME chain length showed a long dependence on the binary diffusion parameters and kinematic viscosity, which are mass and momentum transport properties. Moreover, the vaporization enthalpy of these compounds was directly correlated with the solubilization limits

New Renewable and Biodegradable Particleboards from Jatropha Press Cakes

The influence of thermo-pressing conditions on the mechanical properties of particleboards obtained from Jatropha press cakes was evaluated in this study. Conditions such as molding temperature and press cake oil content were included. All particleboards were cohesive, with proteins and fibers acting respectively as binder and reinforcing fillers. Generally, it was the molding temperature that most affected particleboard mechanical properties. The most resistant boards were obtained using 200°C molding temperature. Glass transition of proteins then occurred during molding, resulting in effective wetting of the fibers. At this optimal molding temperature, the best compromise between flexural properties (7.2 MPa flexural strength at break and 2153 MPa elastic modulus), Charpy impact strength (0.85 kJ/m²) and Shore D surface hardness (71.6°), was a board obtained from press cake with low oil content (7.7%). Such a particleboard would be usable as interlayer sheets for pallets, for the manufacture of containers or furniture, or in the building trade

Chemisorption of molecular oxygen on Cu(1 0 0): a Hartree¿Fock and density functional study

The interaction of molecular oxygen with the Cu(1 0 0) surface has been studied by using both Hartree–Fock and density functional methods in the framework of the cluster model approach. In this study, we have used the Cu8(6,2) cluster in order to simulate the O2 molecular adsorption on different high symmetry chemisorption sites (top–top, bridge–fourfold, bridge–top, fourfold–fourfold) on the Cu(1 0 0) surface. High level non-local density functional (NLSD) computations indicate that the more stable chemisorption site is the bridge–bridge followed by the top–top, bridge–top and bridge–fourfold ones. The calculated 1s O XPS shifts are in good agreement with the experimental indications.Postprint (published version

Chemisorption of molecular oxygen on Cu(1 0 0): a Hartree¿Fock and density functional study

The interaction of molecular oxygen with the Cu(1 0 0) surface has been studied by using both Hartree–Fock and density functional methods in the framework of the cluster model approach. In this study, we have used the Cu8(6,2) cluster in order to simulate the O2 molecular adsorption on different high symmetry chemisorption sites (top–top, bridge–fourfold, bridge–top, fourfold–fourfold) on the Cu(1 0 0) surface. High level non-local density functional (NLSD) computations indicate that the more stable chemisorption site is the bridge–bridge followed by the top–top, bridge–top and bridge–fourfold ones. The calculated 1s O XPS shifts are in good agreement with the experimental indications

Electrochemical Reduction of G3-Factor Endoperoxide and Its Methyl Ether: Evidence for a Competition between Concerted and Stepwise Dissociative Electron Transfer

The reduction of the bicyclic G-factor endoperoxides G3 and G3Me was studied in N,N-dimethylformamide using cyclic voltammetry and convolution analysis. Electron transfer leads to irreversible cleavage of the OO bond. Detailed analysis of the voltammetry curves reveals a non-linear dependence on the transfer coefficient indicating a mechanistic transition from a stepwise mechanism to one with more concerted character with increasing potential. By using quantum calculations to estimate the OO bond dissociation energies, the experimental data was used to evaluate the standard reduction potentials and other pertinent thermochemical information

First computational evidence of a competitive stepwise and concerted mechanism for the reduction of antimalarial endoperoxides

We study structural analogues of endoperoxides belonging to the family of G factors which present moderate to good antimalarial activity. Their biological activity is related to the reduction and cleavage of the O-O bond. Generally, the O-O bond reduction of model endoperoxides, as well as artemisinin, occurs by a concerted dissociative electron transfer (ET) mechanism. For the G3 and G3Me compounds, the experimental counterpart indicates an unexpected competition between a concerted and a stepwise mechanism, but no intermediate species can be isolated. We thus perform DFT studies on the reduction of G3 and G3Me compounds. We confirm the formation of an intermediate radical anion followed by cleavage of the O-O bond in a second step. We characterize the stable conformations for the radical anions G3 •- and G3Me•- resulting from the ET and the associated reaction pathway. We also calculate the reorganization energy upon ET in relation to the Marcus theory using the DFT method. These results provide valuable insight into understanding the biological activity of G-factor endoperoxides as potential therapeutic antimalarial agents