I. Yu. Dmitriev

Electroactive hydrogels based on poly(acrylic acid) and polypyrrole

This study is concerned with the preparation of novel composite systems in which the hydrogel of crosslinked poly(acrylic acid) is a matrix and polypyrrole is an electroconducting component. The effects of synthesis conditions on the structure of the composite systems, their ability to swell in water, and mechanical characteristics are studied. The proposed synthesis procedure allows production of a bulk electroconducting phase of polypyrrole in the hydrogel matrix. The effect of crosslink density of hydrogel on the character of polypyrrole distribution in the matrix is studied. The above composites combine the electrical characteristics of polypyrrole with high elasticity and the ability to repeatedly swell the crosslinked poly(acrylic acid).

Polymorphic transformations in poly(vinylidene fluoride) films during orientation

The effect of uniaxial orientational drawing and isometric annealing on the ratio of polymorphic modifications in the crystalline phase of poly(vinylidene fluoride) is studied. The role of drawing temperature and draw ratio in the structural rearrangements during polymer deformation is analyzed. The conditions providing the highest content of the polar crystalline phase in the polymer are determined. The mechanical properties of the films drawn at different temperatures are investigated.

Electrochemical activity and structure of new composite systems based on cross-linked polyacrylamide and polyaniline

A procedure was developed for preparing electroactive composite systems based on polyacrylamide hydrogel and a conducting polymer, polyaniline. The overall electrical conductivity of the composite systems was measured by chronoamperometry, and the contributions of the electronic and ionic constituents were calculated. The specific capacity of the composites was calculated using galvanostatic charge-discharge cycles, and the stability of the capacity at cycling was evaluated.

Barrier properties and structure of inorganic layers at polyaniline–steel interface

Anticorrosive properties of inorganic layers formed on the surface of steel upon deposition of polyaniline doped with hydrochloric, sulfuric, or phosphoric acid were studied. It was found that the strongest anticorrosive protection is provided by the polymer containing chloride ions. An X-ray phase analysis demonstrated that the high packing order of chains of polyaniline doped with hydrochloric acid leads to formation of an inorganic barrier layer constituted by closely packed iron oxides and hydroxides. Application to the steel surface of polyaniline doped with sulfuric and phosphoric acids results in that barrier layers with weaker anticorrosive properties are formed. It is shown that, in the course of catalytic oxidation of iron by oxygen in the presence of polyaniline, there occur transitions between the emeraldine and pernigraniline forms of the polymer. IR spectroscopy confirmed that polyaniline doped with hydrochloric acid is the most active catalyst for steel surface oxidation.

Anticorrosion activity of aniline–aniline-2-sulfonic acid copolymers on the steel surface

The structure and barrier properties of layers formed on the interface of steel with aniline–orthanilic acid copolymers of different compositions were determined. The structure of the protective system ensuring the best anticorrosion properties was found.

Structure and electric conductivity of copolymers of aniline and aniline-2-sulfonic acid obtained via chemical oxidative copolymerization

A method for the synthesis of aniline-aniline-2-sulfonic acid copolymers is developed. It is shown that the sulfonated polyaniline is capable of self-doping, as evidenced by higher stabilities of the structure and electric conductivity of the copolymers than those of the homopolymer. The mechanism of electric conductivity of the copolymers depends on the comonomer ratio in the feed. By means of the method of impedance spectroscopy, it is found that a decrease in electric conductivity with an increase in the degree of sulfonation is primarily due to reduction in the order of the copolymer structure.

Hybrid hydrogels based on cross-linked polyacrylic acid and polyvinyl alcohol as electrically controlled artificial muscles

A procedure was developed for preparing hybrid hydrogel specimens of preset configuration from cross-linked polyacrylic acid and polyvinyl alcohol. The specimens exhibit higher mechanical characteristics compared to hydrogels of cross-linked polyacrylic acid. Hydrogel specimens fabricated in the form of elastic rings demonstrate an electromechanical response, contraction on passing electric current through their cross section. This effect is more pronounced for the specimens swollen in a sodium sulfate solution than for those swollen in distilled water. The results obtained show that the hydrogels can be used as a linearly operating mechanical force generator (artificial muscle).

Molecular mobility of poly(vinylidene fluoride) in the anisotropic state

The effect of uniaxial orientational drawing and subsequent isometric annealing on the molecular mobility of poly(vinylidene fluoride) was studied by dielectric spectroscopy and dynamic mechanical analysis. The influence of orientation, the polymorphic composition of the crystalline phase, and the structure of disordered regions on dielectric and mechanical relaxation in isotropic and oriented samples was investigated.

Dependence of the dielectric constant on the structure of extruded polyvinylidene fluoride films

The structure of extruded polyvinylidene fluoride films obtained at different die drawing ratios and melt temperatures was studied by X-ray scattering, differential scanning calorimetry, and gravimetry. Their dielectric constant and mechanical properties were examined. The influence exerted by the structure of the amorphous phase and by the molecular weight of the polymer on the dielectric constant of the samples was revealed.

Electromechanical Response and Structure of Chitosan–Polyaniline Composite Systems

Swelling chitosan–polyaniline composite systems demonstrating a pronounced electromechanical response are obtained. The formation of a crosslinked structure in chitosan allows one to enhance elasticstrain properties of composites, but this is accompanied by a decrease in the bending angle under an electric field. Polyaniline as an electroactive component improves the composite system capability of deformation induced by an electric field. The factors contributing to the deformation value are investigated.