Anatolii V. Vannikov

Spectroelectrochemical study of vacuum deposited polyaniline films subjected to postdeposition treatment by HNO3

Abstract Thin polyaniline (PAN) films were prepared by evaporation of emeraldine base in vacuum at 275–325°C, followed by deposition of the vapors onto SnO 2 –glass transparent electrodes. With the purpose to restore the original structure of the polymer, the films were subjected to a postdeposition oxidative treatment in HNO 3 according to the following three different procedures: (1) treatment in vapors of 10 M acid, (2) treatment in 2 M HNO 3 aqueous solution, (3) cyclic treatment: in 2 M aqueous HNO 3 , then in 2 M aqueous NH 3 and so on. Electrochemical and spectroelectrochemical characteristics, namely cyclic voltammetry curves at different sweep rates and optical spectra at stationary potentials, were investigated for these films. It was found that the above characteristics of the films oxidized according to the cyclic procedure are most close to those of conventional PAN. However, in the optical spectra recorded at 0.0 V (vs. Ag/AgCl) for all the vacuum deposited films no absorption band in the area longer than 800 nm was observed. The results are discussed in terms of correlation of changes in the spectroelectrochemical characteristics with formation of heterogeneous structure of PAN by means of arising of intermolecular interactions, as well as, with specific features of vacuum the deposited PAN films.

Investigation of the electrical conductivity of polystyrene under irradiation

A kinetic study has been made of the attainment and decay of electrical conductivity induced in polystyrene irradiated with accelerated electron pulses. The behaviour of the rapid and slow constituents of the delayed component has been investigated, whilst varying the electric field. The effect of the irradiation dose on electrical conductivity induced in strong electric fields (⩾ 5 × 105 V/cm) has been ascertained. The computer calculations show that the rapid constituent of a delayed component with a hyperbolic decay constant of 0.2 μsec may be accounted for satisfactorily in the framework of the Rouse-Fowler model, provided that the traps are small enough (liberation times not exceeding 100 nsec).

On the reversible change in the electrical conductivity of a polyimide during pulsed irradiation

A kinetic study has been made of the attainment and decay of electrical conductivity excited in a polyimide irradiated with fast electron pulses (particle energy 8 MeV, 40 nsec and 2 μsec pulses). It has been found that the delayed component of the radiation induced electrical conductivity consists of fast (τ12=150 nsec) and slow (τ12=2 μsec) components. It is proposed that the fast component is related to a rearrangement of captured charges from shallow to deeper traps, while the slow component is responsible for the experimentally observed inhomogeneous character of the recombination of charge carriers created in the polyimide by irradiation. It is shown that relaxation of induced electrical conductivity after the cessation of irradiation is not a function of the electric field voltage. An estimate of the captured charge drift mobility at room temperature gives μdr=3·6×10−7 cm2/W·sec.

The influence of structure and of chemical formation of polymers on their radiation-pulsed electrical conductivity☆

Abstract Radiation-pulsed electrical conductivity levels have been investigated for a wide variety of polymeric materials. It is shown that a reduction in the degree of crystallinity or the presence of side polar groups in the monomer units of a polymer (involving a consequent increase in the dipole moment of the latter) results in a lowering of the instantaneous conductivity component. It is proposed that the regularities observed stem from the probability of capture of charge-carriers increasing as the amorphous phase content and the dipole moment for a monomer unit are increased. In slightly polar polymers as opposed to apolar some amplitude increase is observed for the delayed component as well as a reduction in the semi-decay time.

Research in the field of 2,4,5-triarlyimidazoles Communication 4. Photobleaching of solutions of 1,4-bis(4,5-diphenyl-2H-imidazol-2-ylidene)-2,5-cyclohexadiene

Conclusions1.Photobleaching of solutions of 1,4-bis(4,5-diphenyl-2H-imidazol-2-ylidene)-2,5-cyclohexadiene (I) proceeds under the influence of UV light withλexc ∼∼365 nm, this process being photosensitized.2.The photosensitizer of this photochemical reaction, which is also a product of the reaction, is 1,4-bis(4,5-diphenyl-lH-imidazol-2-yl)benzene.

Photochrome behavior of methoxy-substituted spiropyrans in acetone solution

Conclusions1.Irradiation of acetone solutions of spiropyrans with an OCH3 substituent in the 8 position leads to the formation of a stable colored form. The absorption band for this form appears only in the spectra of ketone solutions.2.The formation this stable colored form proceeds with the absorption of light by an intermediate spiropyran form, the quantum yield for this process being 0.14.

Photographic and radiation coloration of polymeric layers that contain spiropyrans

1. n nA rapid transformation of the induced spectrum with time fails to occur in polymeric films that contain a spiropyran, which testifies to the absence of transitions between the stereoisomers of the merocyanine form of the spiropyran. n n n n n2. n nThe radiation-chemical yield of the merocyanine form is higher in those matrices where T-T transfer of the energy is accomplished more efficiently.

The photo-decolourization of spiropyranes in polymer matrices☆

An “inverse” photo-chromism (photo-decolourization) has been found in the case of indolinospiropyranes having an electron donating substituent in 6′- and any other type of substituent in 8′-position in polar solvents and polymeric matrices. The quantum yield of the photo-decolourization in visible light has been found to increase with the spiropyrane content. Rapid spectroscopy confirmed the existence of a pigmented form in a photo-excitation of stereo-isomers.