Synthesis of Nanotitania on the Surface of Titanium Metal in Ionic Liquids: Role of Water Additions

The anodic oxidation of a titanium metal electrode in two ionic liquids was studied of amorphous titania nanostructures were obtained. The nanostructures are formed only in the case where a hydrophilic ionic liquid (1-butyl-3-methylimidazolium chloride) with addition of some water is used as the electrolyte. The role of water is to provide a sort of construction material (source of oxygen) for titania nanostructures. In the hydrophobic ionic liquid (1-butyl-3-methylimidazolium), the thickness of the anodic oxide increases and no nanostructures are formed.     

Acrylamide polymers with covalently linked zinc(ii)tetraphenylporphyrin groups: synthesis and complexation with amino acids

1. Download high-res image (96KB)
2. Download full-size image

     

Spin Trapping Studies of Amine-Stabilized Trialkylborane Free Radical Initiator Systems: Kinetics and Mechanism

The free radical initiation chemistry of highly reactive trialkylboranes (R₃B, R?=?n-butyl), stabilized by complexation to amines (A?CR₃B), has been investigated using spin trapping methods and electron paramagnetic resonance spectroscopy. Protonation of A?CR₃B leads to release of R₃B and its subsequent autooxidation in the presence of molecular oxygen. This reaction provides highly reactive alkyl and alkoxy radicals for initiation of ???Colefin polymerization. Kinetic traces of the R₃B autooxidation reaction were obtained by monitoring the relative concentrations of trapped radical species as a function of time for several different initial conditions (acid concentrations). Analysis of a representative kinetic run is discussed in terms of several proposed mechanisms from the literature.     

Conformational and optical properties of macromolecules of some aliphatic-substituted cellulose esters

Synthesized cellulose pelargonates, tridecanoates, valerates, and acetovalerates of various molecular weights are studied in chloroform, dioxane, and tetrachloroethane solutions by the methods of isothermal translational diffusion, sedimentation velocity method, flow birefringence (dynamooptical Maxwell effect), viscometry, and equilibrium electric birefringence (Kerr effect). The equilibrium polymer rigidities are determined and the role of the solvent and temperature in the formation of the conformational characteristics of the macromolecules under study is analyzed. The values of the intrinsic optical anisotropy of the monomeric units of the studied cellulose esters are experimentally determined. The contribution of the side chains to the optical anisotropy of the macromolecules of cellulose esters with aliphatic substituents is analyzed. The results obtained in this study are compared with the data on the cellulose esters with the aliphatic side substituents studied earlier. For the studied samples, the values of the longitudinal components of the monomeric unit dipoles in a nonpolar solvent are estimated.     

Study of structuring of surface-modified technical-grade carbon particles with metal oxides in oligo(divinyl-isoprene)

Effect of a nanosize coating of technical-grade carbon particles with metal oxides NiO, CuO, PbO, and Bi₂O₃ on processes in which continuous carbon structures are formed in an oligomer formulation was studied. The elastic and dissipative constituents of rheological properties of the 3D carbon structures being formed were determined. An optical method and computerized data processing yielded data on structuring of a filled oligomer system under various testing conditions.     

Optical, dynamic, and electro-optical properties of poly(N-acryloyl-11-aminoundecanoic acid) in solutions

The optical, electro-optical, and dynamic characteristics of poly(N-acryloyl-11-aminoundecanoic acid) in organic solvents and of the sodium salt of its monomer in water were studied via the methods of flow birefringence, equilibrium and nonequilibrium electric birefringence, and dynamic light scattering. It is shown that, in aqueous solutions, the monomer forms coarse particles of both symmetric and asymmetric shapes. The linear dimensions of these particles are estimated from the data of translational and rotational diffusion. Polymer macromolecules in organic solvents feature negative anisotropy of optical polarizability. Contributions of optical microform and macroform effects to the observed flow birefringence are analyzed in detail. The intrinsic optical anisotropy of the monomer unit of the polymer, which correlates well with the corresponding values for comb-shaped polymers of a similar structure, is estimated. It is shown that polymer molecules lack marked intrinsic permanent macromolecular dipoles and that electric birefringence in their solutions is associated with macroscopic induced dipole moments that appear during orientation of the dipole moments of polar groups in side chains of the polymer under application of an electric field.     

A locally nonequilibrium model of long-range action during ion irradiation

Based on the principles of extended irreversible thermodynamics, the order parameter characterizing the nonequilibrium of a medium is introduced, and the equations describing the processes of generation and propagation of point defects in irradiated dislocation-free materials are obtained. With the use of a mechanical analogy, the steady-state solutions of the obtained equations are investigated.     

Control of the motion of nanoelectromechanical systems based on carbon nanotubes by electric fields

A new method is proposed for controlling the motion of nanoelectromechanical systems based on carbon nanotubes. In this method, a single-walled nanotube acquires an electric dipole moment owing to the chemical adsorption of atoms or molecules at open ends of the nanotube. The electric dipole moments of carbon nanotubes with chemically modified ends are calculated by the molecular orbital method. These nanotubes can be set in motion under the effect of a nonuniform electric field. The possibility of controlling the motion of nanoelectromechanical systems with the proposed method is demonstrated using a nanotube-based gigahertz oscillator as an example. The operating characteristics of the gigahertz oscillator are analyzed, and its operation is simulated by the molecular dynamics method. The controlling parameters and characteristics corresponding to the controlled operating conditions at a constant frequency for the system under investigation are determined.