O. A. Pyshkina

Conformational Behavior of Giant DNA through Binding with Ag+ and Metallization

The conformational behavior of a long single-chain double-stranded DNA in solutions of free silver ions and silver nanoparticles generated via the reduction of AgNO3 by NaBH4 was monitored by fluorescence and electron microscopies and UV spectroscopy. The interaction of monovalent silver ions with DNA induces shrinking of a DNA-coiled polymer chain as a result of a decrease in the DNA persistence length through the complexation of Ag+ with DNA bases. In contrast, the reduction of silver ions by NaBH4 in DNA solutions triggers DNA compaction: a DNA transition from elongated coil state into a compact state. This transition is continuous, unlike the all-or-none discrete DNA compaction that is commonly seen with multications. It is suggested that the collapse of DNA is accompanied by growth aggregation of silver nanoparticles generated on the DNA template.

Nanoreactor-Assisted Polymerization Toward Stable Dispersions of Conductive Composite Particles

We demonstrate the functioning of a macromolecular nanoreactor which guides a reaction in a confined volume and leads toward improved functional properties of a product material. In our approach, the polymerization of aniline (ANi) is conducted within the interfacial volume of spherical polyelectrolyte brushes (SPB) which are densely affixed to colloidal particles. The SPB provide optimal conditions for matrix polymerization by the efficient confinement of ANi monomers within the finite volume of polyelectrolyte brushes and controlled delivery of the oxidizing reagent to the reaction volume. The excellent kinetic stability of the resulting core-shell particles together with the high macroscopic conductivity of the respective composite open up perspectives for novel materials (a conductive ink).

Synthesis of conducting polyaniline—polyanion interpolymer complexes and study of their composition and properties

The polymerization of aniline in the presence of poly(4-styrenesulfonic acid) and poly(2-acryla-mido-2-methyl-1-propanesulfonic acid) results in interpolyelectrolyte complexes with a composition and a dispersion stability depending on the aniline-to-polyanion ratio in the initial reaction mixture. As opposed to polymerization mediated by poly(4-styrenesulfonic acid), the template polymerization of aniline conducted in the presence of poly(2-acrylamido-2-methyl-1-propanesulfonic acid) leads to the structural template effect that manifests itself as the formation of polyaniline containing 1,2- and 1,4-substituted benzene rings. It is found that the electron conductivity of the polyaniline-polyanion interpolyelectrolyte complexes depends not only on the content but also on the nature of the used polyacid and proves to be higher in the case of stoichiometric interpolyelectrolyte complexes formed in the presence of poly(4-styrenesulfonic acid).

Matrix Synthesis of Water-Soluble Polyaniline in the Presence of Polyelectrolytes

The matrix polymerization of aniline hydrochloride in the presence of polyanions with different chemical structures and molecular masses is studied. Poly(2-acrylamido-2-methyl-1-propanesulfonic acid) and poly(4-styrenesulfonic acid) or its sodium salt are used as polyelectrolyte matrices. It is shown that, if the polymerization of aniline hydrochloride is conducted in the presence of a polyelectrolyte matrix, water-soluble polyelectrolyte complexes in which polyaniline occurs in the form of an emeraldine salt are formed. The mechanism of polymerization is advanced. It is found that the sizes of polyaniline complexes in water are independent of the molecular mass of the polyelectrolyte matrix and its chemical structure.

Effect of polyaniline particle size on the properties of a polyaniline-nylon 6 composite

A method is proposed for the preparation of a conducting polyaniline-nylon 6 composite with controlled morphology of its surface. The method consists of the ammonium persulfate-induced oxidation polymerization of aniline in the presence of nylon 6. As has been established with the use of atomic force microscopy, spherical polyaniline particles are formed on the surface of nylon 6 and their sizes decrease with an increase in the duration of nylon 6 hydrothermal modification at 100° C. It is shown that a decline in polyaniline particle size in the polyaniline-nylon 6 composite enhances its reactivity with respect to KI.

Behavior of multiwalled carbon nanotubes functionalized with sulfo groups in aqueous salt solutions

The functionalization of multiwalled carbon nanotubes (MWCNTs) with sulfanilic acid through the diazotization reaction, which yielded the covalent bonding of sulfo groups to the nanotube surfaces, was performed. Stable aqueous nanotube dispersions were obtained. The sizes of functionalized nanotubes in aqueous salt and salt-free solutions and their hydrodynamic characteristics were measured by dynamic light scattering. The data were compared with the data of scanning electron microscopy.

Molecular properties of sulfonated polyaniline

The molecular characteristics of internally doped sulfonated polyaniline with a sulfonation degree of ∼1 are studied by the methods of viscometry and dynamic light scattering. In diluted aqueous-saline solutions, the molecules of sulfonated polyaniline are individual entities; they do not form intermolecular associates and do not dissociate into separate components. An increase in the concentration of NaCl in solution from 0 to 1 mol/l brings about a sharp gain in the intrinsic viscosity of the polymer and in the hydrodynamic radius of molecules. This effect results from the decomposition of zwitterion pairs responsible for the compact conformation of polymer molecules in water. The equilibrium rigidity of sulfonated polyaniline molecules is calculated from the hydrodynamic characteristics determined in a 1 M NaCl solution, where the electrostatic interaction may be considered to be suppressed. A length of the Kuhn segment of 1.46 nm is higher by a factor of 1.5 than the corresponding length for the initial polyaniline.

Electrically conducting polymeric microspheres comprised of sulfonated polystyrene cores coated with poly(3,4-ethylenedioxythiophene)

Oxidative chemical polymerization of 3,4-ethylenedioxythiophene was carried with 5.8-μm sulfonated polystyrene latex particles as template. Polymerization led to formation of poly(3,4-ethylenedioxythiophene) distributed over the surface of template particles. Increase in initial monomer concentration resulted in the change of poly(3,4-ethylenedioxythiophene) morphology from isolated clusters to continuous 0.2–0.5-μm-thick surface shells. Structure of poly(3,4-ethylenedioxythiophene) coatings had crucial influence on the surface charge and macroscopic electrical conductivity of composite latex particles.

Complexes of Nucleic Acids with Oppositely Charged Amphiphilic Ions in Aqueous and Organic Solutions

The published data on the interaction of DNA macromolecules with cationic amphiphiles (surfactants) are analyzed. The effect of the structure of surfactant molecules on their interaction with DNA and the structure of DNA-surfactant complexes is examined. The unique property of DNA molecules to preserve the double-helix conformation in complexes is considered. The structure of DNA-surfactant complexes in aqueous and organic solutions is discussed, and examples of the possible application of these complexes are presented.

Effect of Multiwall Carbon Nanotubes Surface on Polymerization of Aniline and Properties of Its Products

The effect of surface of multiwall carbon nanotubes on the course of oxidative polymerization of aniline has been studied. In the presence of amorphous carbon fragments at the nanotubes surface, the polymerization at the monomer: nanotubes mass ratio of 10 : 1 yields the composite based on polyaniline and carbon nanotubes. At the same components ratio, carbon nanotubes purified of amorphous carbon inhibit polymerization of aniline, and the process results in oxidation of the nanotubes surface; however, at the lower purified nanotubes content the polymerization proceeds to give the polyaniline/nanotubes composite. Purification of the nanotubes of amorphous carbon significantly enhances electrochemical stability of their composites with polyaniline.