RESUMEN
In the present work, we have investigated concentration and temperature dependences of electrical conductivity of graphite nanoplatelets/epoxy resin composites. The content of nanocarbon filler is varied from 0.01 to 0.05 volume fraction. Before incorporation into the epoxy resin, the graphite nanoplatelets were subjected to ultraviolet ozone treatment at 20-min ultraviolet exposure. The electric resistance of the samples was measured by two- or four-probe method and teraohmmeter E6-13. Several characterization techniques were employed to identify the mechanisms behind the improvements in the electrical properties, including SEM and FTIR spectrum analysis.It is established that the changes of the relative intensities of the bands in FTIR spectra indicate the destruction of the carboxyl group -COOH and group -OH. Electrical conductivity of composites has percolation character and graphite nanoplatelets (ultraviolet ozone treatment for 20 min) addition which leads to a decrease of percolation threshold 0.005 volume fraction and increase values of electrical conductivity (by 2-3 orders of magnitude) above the percolation threshold in comparison with composite materials-graphite nanoplatelets/epoxy resin. The changes of the value and behavior of temperature dependences of the electrical resistivity of epoxy composites with ultraviolet/ozone-treated graphite nanoparticles have been analyzed within the model of effective electrical conductivity. The model takes into account the own electrical conductivity of the filler and the value of contact electric resistance between the filler particles of the formation of continuous conductive pathways.
RESUMEN
[Bis(tri-methyl-sil-yl)amino](tert-butyl-imino)-thio-phospho-rane reacts in benzene with isopropyl alcohol via 1,2-addition of an (i) PrO-H bond across the P=N bond, resulting in the title compound, C13H35N2OPSSi2. In the mol-ecule, the P atom possesses a distorted tetra-hedral environment involving two N atoms from (Me3Si)2N- and (t) BuNH- groups, one O atom from an (i) PrO group and one S atom, therefore the mol-ecule has a stereocenter on the P atom but crystal symmetry leads to a racemate. In the crystal, a pair of enanti-omers form a centrosymmetric dimer via a pair of N-Hâ¯S hydrogen bonds.
RESUMEN
A new range of tin-based reversible addition-fragmentation chain-transfer (RAFT) agents is described and evaluated for the polymerization of acrylamides, methyl acrylate and styrene. These organometallic compounds are highly reactive reversible transfer agents which allow an efficient control of the polymerization of substituted acrylamide monomers, whereas RAFT control for methyl acrylate and styrene polymerization is contaminated by side reactions at prolonged reaction times. 119Sn NMR is shown to be an informative instrument for the monitoring of Sn-RAFT-mediated polymerizations.
RESUMEN
The centrosymmetric tetranuclear title molecule, [Sn4(C3H7O)4Cl4O2], contains two types of Sn atoms, Sn(II) and Sn(IV). The Sn(II) atom has a trigonal-pyramidal coordination environment and is bonded to two O atoms from two iso-propano-late groups and one µ3-oxide atom. The Sn(IV) atom has an octa-hedral coordination environment, formed by two chloride atoms, two µ3-oxide atoms and two O atoms from iso-propano-late groups.
RESUMEN
In the title compound, [Ge(C(9)H(11)O)(2)(C(6)H(16)N(2))], the Ge(II) atom is coordinated in a distorted trigonal-pyramidal geometry by two O atoms belonging to two 2,4,6-trimethyl-phenolate ligands and one N atom of a tetra-methyl-ethylenediamine ligand. Comparing the structure with published data of similar compounds shows that the Ge-O bonds are covalent and the Ge-N bond is coordinated.
RESUMEN
The binuclear centrosymmetric title compound, [Sn(2)(C(3)H(7)O)(6)Cl(2)(C(3)H(8)O)(2)], exhibits an edge-shared double octahedral exhibits an edge-shared octa-hedral structure, which is distorted owing to the presence of asymmetric intra-molecular hydrogen bonds between the axially coordinated isopropanol and isopropoxide ligands. The H atom of the hy-droxy group is located nearer to an isoprop-oxy group with the longest Sn-O bond [2.1789â (17)â Å].
RESUMEN
The low-coordinate phosphorus compounds (Me(3)Si)(2)N-P=NSiMe(3), (Me(3)Si)(2)N-P(=S)=N(t)Bu and (Me(3)Si)(2)N-P(=NSiMe(3))(2) react with ((i)PrO)(3)M≡M(O(i)Pr)(3) (M = Mo, W) to form four- and five-membered metallacycles with intact endocyclic or exocyclic M≡M triple bonds. The first four-membered planar metallacycles, containing an M≡M triple bond were obtained in reaction with (Me(3)Si)(2)N-P=NSiMe(3).