Effect of chemical modification of ion-exchange membrane MA-40 on its electrochemical characteristics

Transport characteristics of commercial heterogeneous anion-exchange membranes MA-40 and MA-41 are studied, together with those of membrane MA-40M fabricated by treating the MA-40 surfaces with a strong polyelectrolyte complex. It is demonstrated that, after modification, the electrical conductivity of MA-40M in an NaOH solution increases. At overlimiting currents, the water dissociation rate on this membrane decreases as compared with the initial membrane. At the same time, no noticeable change in the rate of transport of counter-ions (ions Cl^-) through the membrane at a fixed potential drop is discovered at under-and overlimiting currents. The MA-40M membrane behavior is explained by the conversion of secondary and tertiary functional ammonium groups in the near-surface membrane layers approximately 80 μm thick into quaternary groups during the treatment by the polyelectrolyte.     

New Synthetic Approach to Phosphonium Salts Derived from 4,5-Bis(diphenylphosphino)-1-phenylpyridazin-6-one and Quantum-Chemical Calculations of Their Formation

4,5-Bis(diphenylphosphino)-1-phenylpyridazin-6-one reacts with ethyl iodide, 1,2-dichloroethane, 1,2-dibromomehtane, and o-dibromobenzene to give the corresponding bis-phosphonium salts which, depend- ing on the halogen derivative, can undergo further transformations involving cleavage of the PÄC bond in the -position with respect to the carbonyl group.     

Characteristics of the radical polymerization of acetylene monomers

The radical polymerization of acetylene monomers is studied via electron spin resonance (ESR) spectroscopy, calorimetry, chromatography, and gravimetry within a wide range of temperatures (77–340 K). A growing macroradical with an unpaired electron localized on the terminal moiety of a macromolecule is shown to lose its activity, due to the delocalization of electron over the conjugated system of double bonds after attaining the very short length of 5–10 monomer units. This explains the low conversion and molecular masses of the synthesized polymers.     

Condensation of resorcinol with phosphorylated acetals, synthesis of calix[4]resorcinolarenes with phosphorus-containing alkyl fragments in the lower rim

The reaction of resorcinol with phosphorylated acetals leads to formation of calix[4]resorcinolarenes having phosphonate, phosphinate, or (phosphinothioyl)sulfanylmethyl fragments in the lower rim of the molecule.     

Crystal structure of α‴-(Zn1−x Cd x )3As2 (x = 0.26)

Single crystals of the α?-phase of (Zn_{1 ? x} Cd _x )₃As₂ solid solution (x = 0.26) have been prepared and investigated by X-ray diffraction analysis. The tetragonal unit-cell parameters are found to be a = b = 8.5377(2) Å, c = 24.0666(9) Å, sp. gr. I4₁/amd, Z = 16. Zn and Cd atoms in the crystal statistically occupy three symmetrically independent positions in the mirror planes and are tetrahedrally coordinated by arsenic atoms. (Zn,Cd) tetrahedra share edges to form a three-dimensional structure framework. The α?-phase is geometrically related to the fluorite structure. The character of arrangement of tetrahedral vacancies in fluorite-like unit cells is revealed. Chains of tetrahedral vacancies form microchannels oriented parallel the a and b axes, which pierce the three-dimensional structure framework at different levels along the c axis. The structure of α″-Cd₃As₂ crystals is found to be similar to that of α?-(Zn_0.74Cd_0.26)₃As₂.     

Macromolecular effects upon enzymatic degradation of chitosan in solution

Macromolecular effects were revealed in the course of enzymatic degradation of chitosan in an acetic acid solution under the action of hyaluronidase, a nonspecific enzyme. It was shown that the concentration of chitosan in the initial solution determines its supramolecular organization and, hence, the degree of enzymatic degradation.     

Direct and initiated halogenation of carbon nanomaterials at low temperatures

Cryochemical reactions of the direct and initiated (by photolysis and radiolysis) halogenation of carbon nanomaterials (C₆₀ fullerene, nanotubes, and nanofibers) at 77–240 K were investigated by the ESR, IR spectroscopy, and elemental analysis techniques. A high reactivity of C₆₀ in reactions with fluorine and chlorine with the formation of corresponding derivatives was shown. High concentrations of radical intermediates indicating the radical chain halogenation of C₆₀ were detected (the kinetic chain length for the chlorination process reaches 10⁴–10⁶ units). The amount of chlorine attached to fullerene is ～35% and practically does not depend on the initiation mode (UV or γ-irradiation at doses up to 350 kGy). The mechanism of the cryochemical halogenation of C₆₀ is considered within the limits of the model of multicenter synchronous transitions in a molecular complex consisting of several reactant molecules including molecular fluorine or chlorine and ensuring a net exothermic effect. The amount of chlorine added to nanotubes and nanofibers did not exceed 2.5–8%, thereby indicating a low reactivity of these materials under cryogenic conditions.