A. A. Grishchuk

Properties of nanocomposites based on crosslinked elastomeric polyurethane and ultrasmall additives of single-wall carbon nanotubes

It is shown for the first time that the addition of ultrasmall amounts of single-wall carbon nanotubes leads to a significant increase in the main mechanical characteristics of the crosslinked poly(urethane urea) elastomer. The elastic modulus and the tensile strength pass through maxima as the nanotube concentration is increased from 0 to 0.018 wt %; at a nanotube concentration of 0.002 wt %, the maximum values of the modulus and strength are higher by factors of 2.5 and 1.5, respectively, than the corresponding values for the unfilled polymer. The thermomechanical, spectral, and structural characteristics of nanomodified elastomers are investigated, and possible causes of change in their mechanical parameters are discussed.

Study of the influence of single-wall carbon nanotube dispersion techniques upon the properties of epoxy resin-based nanocomposites

A comparison of two techniques, ultrasonication and the controlled wave treatment, for the dispersion of ultra-small concentrations of carbon nanotubes in epoxy resin has been carried out with specially designed instruments. Studies with optical microscopy and physicomechanical and thermomechanical tests showed that both techniques provide almost equal degrees of nanotube dispersion in the matrix and dependences of the basic physicomechanical properties of cured epoxy polymers on the nanofiller concentrations. However, the difference between the two techniques has been shown at the study of the structural properties of the cured epoxy polymers (the molecular weight of the internode chains of the polymeric network, and the vitrification temperature), which are more stable in the case of the wave treatment. Thus, wave treatment is a promising dispersion technique, and it is applicable at the industrial scale because it is almost unlimited by the size and capacities of the equipment.

Synthesis of (polycyanoisopropyl)[60]fullerene

The reaction of fullerene with excess 2,2′-azobis(isobutyronitrile) in o-dichlorobenzene at 60°C was studied, and the chemical structure of the reaction product was determined.

Regularities of the formation of silver nanoparticles with oligostyrylcarboxylate ligands

Regularities of the formation of silver nanoparticles with oligostyrylcarboxylate ligands during the one-step reduction of silver oligostyrylcarboxylates with triethylamine are studied via UV–Vis and IR spectroscopy. It is shown that the synthesis of silver nanoparticles occurs in a system with micellar organized molecules of the oligomeric precursor–ionomer. The formation of silver nanoparticles occurs through the successive formation of a diphilic silver oligostyrylcarboxylate/triethylamine complex, reduction of Ag+ in the cores of reverse micelles with the formation of (Ag0)n nuclei, and their subsequent growth through self-assembly.

Synthesis of water-soluble starlike poly(N-isopropylacrylamides) with fullerene C60 as a multifunctional core

New water-soluble starlike polymers with a fullerene core are synthesized via the radical polymerization of N-isopropylacrylamide in the presence of fullerene C60. The starlike structures of the polymers are studied by the methods of gel-permeation chromatography and scanning-electron microscopy.

Problems in the size exclusion chromatography of poly(N-isopropylacrylamide) on styragel columns

The molecular weights of poly(N-isopropylacrylamide) (PNIPA), calculated according to polystyrene calibration standards upon the elution of THF on styragel columns, appear to be much lower than their actual values determined using independent approaches. This is likely due to interactions between the nitrogen-containing units of PNIPA polymer chains and the sorbent, so the polymer is eluted in the mode intermediate between exclusion and critical. An effective exclusion mode during the elution of PNIPA on a styragel column can be achieved by using an eluent more polar than tetrahydrofuran (particularly, 1-methylpyrrolidone).

Formation of star-like water-soluble polymeric structures in the process of radical polymerization of N-isopropylacrylamide in the presence of C60

The formation of star-like N-isopropylacrylamide (NIPA) polymeric structures in the presence of C60 occurs in two steps. In the polymerization induction period, water-insoluble cores of future star-like polymers (SP) are formed. The cores are composed of one or more C60 molecules linked by a C—C bond, five or six initiator radicals, and several short NIPA polymeric chains. The formation of SP begins after the induction period and continues until the end of polymerization through gradual growth of the polymeric layer at the cores. The solubility of SP in water is determined by a certain initial concentration of NIPA. It is suggested that the mechanism of these processes is determined by a dependence of C60 reactivity on the degree of its “substitution”.

Anionic polymerization and copolymerization of acrylonitrile initiated by systems based on bicyclic tertiary amines and ethylene oxide

It is shown that the products of interaction of ethylene oxide and bicyclic amines containing tertiary nitrogen atoms at the tops of bicyclic structures efficiently initiate the anionic polymerization of acrylonitrile. As opposed to all known initiators of this process, the mentioned initiating systems contain no metal atoms or atoms of elements heavier than oxygen. The polymerization of acrylonitrile under the action of the ethylene oxide–bicyclic amine system in a polar medium (dimethyl sulfoxide) at room temperature occurs in the homogeneous regime over several minutes, while, in a weakly polar solvent (tetrahydrofuran), polymerization occurs in the heterogeneous regime over several hours. The reaction may become homogeneous in a mixture of these solvents at both room temperature and a lower temperature. The number-average molecular masses of the polymers, depending on polymerization conditions, are in the range from 25 × 103 to 480 × 103 and their polydispersity indexes are from 1.55 to ~3.40. It is found that the copolymers of acrylonitrile with oxygen-containing acrylic monomers, as well as with ethylene oxide, can be prepared.

Some trends observed in [60]fullerene polymerization activated by butyllithium isomers

It was found that BuLi plays a dual role in the polymerization of [60]fullerene: the addition of a first molecule of BuLi makes C60 tending to polymerize, while the addition of more BuLi molecules to the other reactive double bonds impedes this process.

“Dormant” inhibitors of urethane type as controllers of temperature modes of styrene polymerization

Urethanes based on a series of monoisocyanates and phenolic inhibitors of styrene radical polymerization, which release the initial phenolic inhibitor at elevated temperatures, were prepared and characterized. Some of these compounds meet the requirements to “dormant” inhibitors: they sharply decelerate thermally initiated high-temperature polymerization of styrene and do not noticeably affect the rate of low-temperature polymerization in the presence of an inhibiting substance. The possibility of preventing uncontrollable emergency situations by adding these compounds to the initial monomer was confirmed experimentally.