Sulfur-containing polymer and carbon materials based on poly(vinyl chloride)

New sulfur-containing copolymers based on poly(vinyl chloride) have been prepared by the nucleophilic substitution of chlorine atoms by sulfur atoms using sodium tetra- and pentasulfides. It has been shown that these copolymers can be carbonized to produce sulfur-containing carbon materials with residual chlorine content about 2 wt %.     

Experimental study of mode selection in shallow-water sea

The possibilities of matching low-frequency underwater sound pulses to the parameters of an oceanic waveguide are considered. The objective is to optimize the system of few-mode tomographic observation in a shallow-water sea. Experimental data are analyzed for two methods of selecting the low-frequency fewmode pulses propagating in a shallow-water sea. The first method excites probe pulses by vertically elongated arrays, with spatial filtering after vertical or horizontal arrays receive the pulses. The second method is based on exciting broadband signals with linear frequency modulation by a single transmitter. The selection of the few-mode signal is performed by time strobing the signals at the output of the matched filter after a horizontal array receives the pulses. The distance between the sound sources and receiving systems varied from 10 to 300 km.     

Simulation of soliton solutions for the propagation of a femtosecond pulse in a medium with a cubic nonlinearity

Soliton solutions are constructed numerically for the problem of propagation of a femtosecond pulse in a medium with a cubic nonlinearity. The problem is posed as an eigenvalue problem with an operator nonlinear in the eigenfunctions. For given values of the propagation parameter we find the real eigenvalue λ and the corresponding eigenvector. This eigenvector is a soliton, i.e., a solution that does not vary in the coordinate of propagation of the light pulse. An algorithm is proposed to find the minimum eigenvalue and the corresponding eigenfunctions that satisfy given conditions. Translated from Prikladnaya Matematika i Informatika, No. 2, pp. 63–68, 1999.     

Strong intramolecular hydrogen bond N—H...O in 2-(2-acyl-1-phenylethenyl)-5-phenylpyrroles

The molecular structure of 2-(2-benzoyl-1-phenylethenyl)-5-phenylpyrrole and 2-(2-furoyl-1-phenylethenyl)-5-phenylpyrrole was studied by X-ray diffraction analysis at 110 K and quantum chemistry methods (B3LYP/6-31G*). In the crystalline state, both compounds have cyclic structures closed by strong intramolecular hydrogen bond N—H...O. Canonic zwitterionic structure contributes largely to the ground state of the molecules. This is probably due to synergism of the H-bonding and -electron interactions.     

Tertiary Phosphine Oxides in Reaction with Benzaldehyde

Symmetrical and unsymmetrical tertiary phosphine oxides containing benzyl and 5-chloro-2-thienyl radicals stereoselectively react with benzaldehyde in the sodium amide-THF system to form the E isomers of 1-organyl-2-phenylethene and diorganylphosphinic acids in high yields. Triethyl, tris(2-phenyl- ethyl)-, and tris[(4-methoxyphenyl)methyl]phosphine oxides under the above-mentioned conditions do not react with benzaldehyde.     

Expedient one-pot organometallics-free synthesis of tris(2-pyridyl)phosphine from 2-bromopyridine and elemental phosphorus

2-Bromopyridine reacts with elemental phosphorus (red or white) in a superbasic KOH/DMSO(H₂O) suspension at 100 °C (for red phosphorus) and 75 °C (for white phosphorus) over 3 h to afford tris(2-pyridyl)phosphine in a 62% yield (from red phosphorus) and a 50% yield (from white phosphorus). Under microwave assistance, the reaction with red phosphorus takes just 20 min to produce tris(2-pyridyl)phosphine in 53% yield. A hitherto unknown complex, [Pd(PPy₃)₂Cl₂]·CH₂Cl₂, synthesized from tris(2-pyridyl)phosphine and PdCl₂, has the cis-configuration; this is unusual for bis(phosphino)palladium dichloride complexes.     

Thermoresponsive star-shaped poly(2-isopropyl-2-oxazolines) based on octa-tert-butylcalix[8]arene

Star-shaped polymers with a central calixarene core and oligo(N-isobutyroylethyleneimine) arms are synthesized with the use of cationic polymerization. The effects of the structure of the initiator, the initiator concentration, and the solvent nature on the structure and molecular-mass characteristics of the polymers are studied. It is shown that the polymers form complexes with low-molecular-mass organic compounds and feature lower critical solution temperatures.     

Nanobiocomposites of Pharmacophoric Iron and Bismuth Oxides with Arabinogalactan Matrix

Water-soluble nanocomposites with narrow distribution of nanoparticles of pharmacophore bismuth and iron oxides have been obtained. The biopolymer matrix of the arabinogalactan polysaccharide has exhibited strong stabilizing properties with respect to transition metal oxides. The size of the spherical metal oxide nanoparticles has been found of 5–7 nm as per transmission electron microscopy. The exclusion liquid chromatography data have revealed that the change in the molecular mass parameters of arabinogalactan is due to the combined processes of self-assembly of nanocomposites and alkaline decomposition.