A. A. Zezin

From triple interpolyelectrolyte-metal complexes to polymer-metal nanocomposites

Nanocomposite polymer materials containing metal or metal oxide particles attract growing interest due to their specific unique combination of physical and electric behavior. Stoichometric triple interpolyelectrolyte-metal complexes (TIMC) are insoluble in water and in aqueous organic media and may include high content of metal ions; concentration of ions is easy to vary in such polymeric systems. Reduction of metal ions is a common method for obtaining nanoparticles. Interpolyelectrolyte complexes reveal high permeability for polar low-molecular substances and salts. Such swelling behavior is important for the reduction of metal ions included in these solids. The properties of triple interpolyelectrolyte-metal complexes and preparation of nanocomposites from these materials using various methods of metal ion reduction are discussed in this work.

Advanced functional structures based on interpolyelectrolyte complexes

This review considers interpolyelectrolyte complexes, with a particular emphasis on advanced macromolecular co-assemblies based on polyionic species with nonlinear topology and on polymer–inorganic hybrids formed by interpolyelectrolyte complexes containing metal ions and/or metal nanoparticles.

Reduction of copper(II) ions in polyacrylic acid-polyethyleneimine complexes using X-ray radiation

The specifics of X-ray-induced reduction of copper(II) ions in the polyacrylic acid-polyethyleneimine-copper(II) (PAA-PEI-Cu2+) complexes were studied. It was found that the action of radiation led to the effective reduction of Cu2+ in the PAA-PEI-Cu2+ films swollen in an aqueous-alcohol medium. The formation of metal nanoparticles in irradiated samples was revealed by electron microscopy and X-ray diffraction techniques. Analysis of ESR data has demonstrated that the Cu2+ reduction rate increases with an increase in the initial concentration of copper ions in the samples. Formal yields of the radiation-chemical reduction of Cu2+ in the PAA-PEI complex films were found to be quite high (>100 ions per100 eV of energy absorbed by the swollen film), which can be explained by involvement of the radiolysis products of aqueous alcoholic solutions (outer medium) in the reduction processes.

Formation of metal-polymer hybrid nanostructures during radiation-induced reduction of metal ions in poly(acrylic acid)-poly(ethylenimine) complexes

The formation of nanoparticles during the radiation-induced chemical reduction of silver ions, copper ions, and nickel ions in films based on poly(acrylic acid)-poly(ethylenimine) complexes are studied via electron microscopy. This approach allows preparation of composites containing nanoparticles that are randomly distributed in the polymer matrix and materials with a regular spatial distribution of nanoparticles across the film thickness and in subsurface layers. The structure of metal-polymer hybrid materials is dependent on the irradiation conditions, the type of reduced metal ions, and their initial content in polymer matrices. The ratio between the rate of nucleation and the rate of growth of nanoparticles in the matrices of interpolyelectrolyte complexes depends on the intensity of the absorbed dose and on the mechanisms of reduction of metal ions and formation of clusters. The IR spectroscopic studies reveal the effect of nanoparticles on the chemical structure of the polymer matrix.

Synthesis of hybrid materials in polyelectrolyte matrixes: Control over sizes and spatial organization of metallic nanostructures

This review is concerned with the synthesis of hybrid materials in solutions, suspensions, and gels of polyelectrolytes with emphasis being placed on the role of interaction between functional groups of macromolecules and ions/surfaces of metals in the control over the processes of nucleation and growth of nanoparticles. The use of several macromolecules carrying nonionogenic groups for the effective control over the sizes and shapes of nanoparticles is exemplified. As the main method for the synthesis of metal nanostructures in colloidal systems, a method based on the reduction of metal ions is discussed. Mechanisms and conditions determining the assembly of metal–polymer nanocomposites of various architectures in polyelectrolyte matrixes and organized polymer systems are considered.

The formation of metal nanoparticles in polyacrylic acid-polyethyleneimine complex upon reduction of copper(II) ions using X-ray irradiation

The features of nanoparticle formation by the radiation-chemical reduction of Cu2+ ions in polyacrylic acid-polyethyleneimine complexes have been studied. It has been shown that the swollen film/aqueous alcohol medium interphase exchange of the reducing species and the specifics of X-ray energy transfer play an important role in the formation of metal particles in the subsurface layer of polymer matrixes. An analysis of EPR and X-ray diffraction data shows that an acetaldehyde admixture increases the Cu2+ reduction rate of and enables the growth of nanoparticles.

Positive Hole Transfer Upon Irradiation of Frozen Alkylbenzene Solutions in Freonic Matrices at 77 K

The process of positive hole transfer between alkylbenzene molecules of various structures occurring upon irradiation in electron-scavenging (freonic) matrices at 77 K was studied by ESR. The factors controlling the efficiency and direction of this process were analyzed. In the case of the ethylbenzene–toluene pair, it was shown that the direction of hole transfer depends on the conformation of the ethylbenzene radical cation. If the conformation effects are absent, the hole transfer occurs in accordance with the gas-phase ionization potentials (IP) and appears to be efficient, provided that the difference in the IP values is greater than 0.3 eV.

Positive hole transfer between organic molecules of different classes in freon matrices

The processes of positive charge (hole) transfer between organic molecules of different classes occurring upon irradiation of their frozen freonic solutions at 77 K were studied by ESR spectroscopy. The efficiency of positive hole transfer was characterized by the “redistribution coefficient”, which was determined as ratio of concentrations of the radical cations of different compounds at equal concentrations of the parent neutral molecules. A very effective positive hole transfer to toluene was shown to occur for alkane-toluene pairs (K > 10). Meanwhile, much lower K values (∼ 2 to 3) were observed for alkane-alkene pairs, in spite of a rather high difference in the ionization potentials (ca. 1 eV). This effect was explained by the conformation dispersion and distribution of environment configurations of ionized molecules for the alkane-alkene pairs. An effective positive hole transfer (K ∼ 6) was observed for the pair dimethyl ether-acetone, where the conformation dispersion was absent, although the difference in ionization potentials for this pair was only 0.3 eV.