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It was found that in the region of the percolation threshold, depending on the dominance of one or another conduction mechanism, the temperature dependence of the specific volume resistivity ρ(T) of the polymer composite based on a matrix of ethylene vinyl acetate is significantly transformed. With an increase in the CB content, there is a decrease by several orders of magnitude in the maximum value of the relative resistivity ρ(T)max/ρ20 in its temperature dependence. Peroxide crosslinking of matrix macromolecules leads to a change in the nature of the temperature dependence of resistivity. [ABSTRACT FROM AUTHOR]

We have studied the influence of the carbon black content on the phase composition of a polymer composite material based on ethylene vinyl acetate. It is established that there exists an additional (high-temperature) crystalline polymer phase the relative fraction of which depends on the content of carbon black. Saturation of the carbonaceous polymer composite with peroxide significantly influences the polymorphism of the material and its electric conductivity. [ABSTRACT FROM AUTHOR]

We have observed significant differences between the temperature dependences of electric resistivity of a carbonaceous polymer composite based on ethylene vinyl acetate and the same composite saturated with peroxide. It is established that there is a quite clear correlation between characteristic points on the temperature dependences of resistivity and the curves of differential scanning calorimetry. [ABSTRACT FROM AUTHOR]

A modified procedure has been developed for the synthesis of Kuhn verdazyl radicals via conversion of 1-(4-R1-phenyl)-3-(4-R2-phenyl)-5-phenylformazan into 1-(4-R1-phenyl)-3-(4-R2-phenyl)-5-phenylver-dazylium tetrafluoroborates, followed by their reduction with D-glucose in alkaline medium to 1-(4-R1-phenyl)-3-(4-R2-phenyl)-5-phenylleucoverdazyls and oxidation of the latter with atmospheric oxygen. The formation of 1-(4-R1-phenyl)-3-(4-R2-phenyl)-5-phenylverdazyl radicals was confirmed by ESR spectroscopy. [ABSTRACT FROM AUTHOR]

The corresponding formazans were synthesized by the reaction of phenylhydrazones of nitro-substituted benzaldehydes and 4-pyridinecarbaldehyde with arenediazonium salts obtained from p-substituted anilines. Formazans were converted into the corresponding 5,6-dihydro-1,2,4,5-tetrazinium triflates by the action of formalin in the presence of CF3SO3H. When tetrazinium salts were treated with D-glucose in a weakly alkaline medium (NH4OH) in the presence of atmospheric oxygen, stable tetrazinyl radicals were formed. Formazans, tetrazinium triflates, and tetrazinyl radicals were isolated in the individual state and characterized by elemental analysis, IR, UV, NMR, or ESR (radicals) spectroscopy. [ABSTRACT FROM AUTHOR]

It is shown that, if the uniform resonance fields in the layers of a two-layer film differ considerably, the spin-wave resonance spectrum consists of two series of peaks corresponding to harmonic spin modes localized in the first and the second layer. This means that effective pinning of spins can be ensured by the layer in the state of a reactive (elastic) medium, as well as by the layer which is a dispersive medium for spin waves. [ABSTRACT FROM AUTHOR]