The method of low temperature ESR spectroscopy was used to study the free radicals generated by -irradiation of crown ethers: 12-crown-4 /1/; 15-crown-5 /2/; dicyclohexane-24-crown-8 /3/; and their analogues: tetrahydrofurane /4/ and 1,4-dioxane /5/. ESR spectra of radicals 4 and 5 taken at 77 K represent a simple singlet; ESR spectra of radicals generated from 1, 2 and 3 have a complex, multiplet structure. The kinetics of thermal decay of free radicals 4 in dependence on temperature starting from 103 K was investigated. The radicals 4 decay very fast at 253 K.
The influence of radioactive krypton85Kr on the surface properties of poly(3-pentylthiophene) has been studied. Irradiation by gaseous85Kr leads to structural polymeric chain changes, which induce after iodine doping the formation of charge-transfer complexes with iodine as well as with gaseous sulfur dioxide manifesting itself by the increased electric conductivity. The presence of ammonia brings about reaction with iodine bound in the complex with a conducting polymer.
Authors:G. Čík, J. Lesný, F. Šeršeň, J. Bartuš, and R. Pecníková
The influence of -radiation on iodinedoped poly (3-pentylthiophene) has been studied. Doping accompanied by -radiation brings about a decrease of iodine release rate. An increased dopant concentration in the poly (3-pentylthiophene) leads to an increased conductivity, which may be accounted for by the formation of bipolarons in the irradiated and doped samples.
The diffusion of sulfur dioxide into partially iodine-doped poly (3-dodecylthiophene) and poly(hexadecylthiophene) has been studied. A direct dependence of the diffusion rate on the alkyl group lengths was ascertained. The diffusion rate could be increased by irradiation of the polymers.
The influence of certain gases on the properties of thermally treated and -irradiated Langmuir-Blodgett (LB) films of poly (3-hexadecylthiophene) and stearic acid has been studied. Both the heat and -radiation brought about some structural surface layer changes, leading to temporal variations of the course of the in-plane conductivity of films affected by the presence of applied gases.
The influence of -radiation on the electric properties of Langmuir-Blodgett (LB) films of partially iodine-doped poly-(3-hexadecylthiophene) and stearic acid in interaction with selected environment-polluting gases has been studied. CO2, CO and NO2 increase the LB films conductivity and NO has a tendency to decrease the electric conductivity. The influence of -radiation was expressive onyl in the case of CO2, whereas NO2 brought about degradation of the conductive polymer.
The magnetic properties of poly(3-dodecyl-thiophene) (PDDT) irradiated by -beams have been studied by measuring the magnetic susceptibility and EPR spectra. The irradiated PDDT is characterized, similarly as the non-irradiated one, by an antiferromagnetic course of magnetic susceptibility with a Néel temperature of 237 K. It is suggested that the antiferromagnetic properties of PDDT are caused by transformation of polarons to bipolarons, which takes place at lower temperatures.
Authors:M. Galamboš, M. Daňo, O. Rosskopfová, F. Šeršeň, J. Kufčáková, R. Adamcová, and P. Rajec
One of the basic prerequisites for the use of bentonite as engineering barrier in deep geological repositories for radioactive
waste and spent nuclear fuel is their stability against ionizing radiation stemming from radionuclides present in radioactive
waste and spent nuclear fuel. The aim of this study was to compare the changes in the adsorption properties of selected Slovak
bentonites in relation to uranium fission products (137Cs and 90Sr), prior to and after irradiation of bentonites with a 60Co γ-source and specifying the changes in the structure of Slovak bentonites induced by γ-radiation. The changes in irradiated
natural forms of Slovak bentonites and the changes in their natrified analogues and fractions with different grain sizes were
studied from five Slovak deposits: Jelšový potok, Kopernica, Lastovce, Lieskovec and Dolná Ves. The EPR spectra of bentonites
from deposits Jelšový potok and Lieskovec with absorbed doses of 104 and 105 Gy γ-rays showed no changes in the structure of the studied Slovak bentonites. The changes, which in terms of structure destabilization
can be considered insignificant, occurred only in bentonites with absorbed doses of γ-radiation as much as 1 MGy. The absorbed
dose of 1 MGy γ-radiation did not have an effect on the adsorption of cesium on every studied bentonite. Changes that can
also be regarded as insignificant occurred only during strontium adsorption, especially on Fe–bentonite from deposit Lieskovec
and Ca–Mg–bentonite from deposit Jelšový potok, when an increase in the adsorption capacity occurred. Attention should be
paid in further research of this topic which would require carrying out experiments on bentonite samples with absorbed doses
higher by several orders of magnitude.