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1
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Some Aspects of Positronium Interaction with Elementary Free Volumes in Polymers

100%
Shantarovich V.
Acta Physica Polonica A
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2001
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vol. 99
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issue 3-4
487-495
EN
This paper contains a discussion of original and recently published results on positronium annihilation lifetime studies of elementary free volumes in the group of polymer glasses. The results are used for indication of non-homogeneity of these materials and give some basis for considering a connection of the long-lived component intensities I_3(I_4) with concentrations N_3(N_4) of elementary free volumes and, in this way, with fractional free volume.
2
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Comments on the Effect ofγ-Irradiation on Positronium Formation in Polymers at Low Temperatures

45%
Shantarovich V., Hirade T., Kevdina I., Gustov V., Oleinik E.
Acta Physica Polonica A
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2001
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vol. 99
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issue 3-4
497-501
EN
Quantitative description of the effect of γ-irradiation of PE and PMMA on positronium formation on the trapped electrons at low temperatures is suggested. The consideration shows that, at least in these substances, the number of the trapping centers is probably enough to localize all ortho-positronium, and therefore the intensity of the long-lived positronium component is dependent mostly on the probability of Ps formation but not on the number of the trapping centers.
3
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The Influence of Deformation and Chemical Composition on Elementary Free Volumes in Glassy Polymers

45%
Shantarovich V., Novikov Y., Suptel Z., Oleinik E., Boyce M.
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vol. 95
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issue 4
659-662
EN
A relation between positronium annihilation characteristics and concentration of elementary free volumes is considered for the case of positronium formation before its localization. We estimated the diffusion coefficient of nonlocalized positronium (≈10^{-4} cm^{2}/s). The positron annihilation lifetime studies of uniaxial compression and annealing of some glassy polymers revealed variations of the shape of elementary free volumes size-distributions.
4
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Application of Coincidence Doppler Broadening Spectroscopy to Hydrocarbons at Different Substance States

39%
Yu R., Suzuki T., Ito Y., Djourelov N., Kondo K., Shantarovich V.
Acta Physica Polonica A
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2005
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vol. 107
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issue 4
697-701
EN
Coincidence Doppler broadening spectroscopy was applied to study n-hexane (C_6H_{14}), cyclohexane (C_6H_{12}) and cyclohexanone (C_6H_{10}O), at solid, as well as liquid states. The experiments were performed in parallel with traditional positron annihilation lifetime spectroscopy. Significant positron trapping by oxygen was observed in cyclohexanone; the oxygen effect is stronger in liquid state than in solid one, which can possibly be attributed to positron solvation in polar solution. Coincidence Doppler broadening results for n-hexane and cyclohexane indicate an existence of higher energetic annihilation electrons in Ps-bubble forming liquids than that in solids.
5
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Nanoporosity of Polymer Sorbents and Membrane Materials as Seen by PALS and Low Temperature Gas Sorption

39%
Shantarovich V., Bekeshev V., Kevdina I., Yampolskii Y., Bermeshev M., Belov N.
Acta Physica Polonica A
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2017
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vol. 132
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issue 5
1548-1551
EN
The limits of application of positron annihilation lifetime spectroscopy and low temperature gas sorption for studying nanoporosity of polymer sorbents and membrane materials are discussed relying on the results previously obtained by the authors. For the two methods, limitations are determined by different factors: the dispersion of the material is essential for low temperature gas sorption, while concentration of nanopores of given size is important for positron annihilation lifetime spectroscopy. The both methods came out to be a useful addition to each other in the studies of micropores and mesopores.
6
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Some Aspects of Free Volume Studies in Molecular Substances Using Positron Annihilation Experiments

39%
Shantarovich V., Suzuki T., Djourelov N., Shimazu A., Gustov V., Kevdina I.
Acta Physica Polonica A
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2005
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vol. 107
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issue 4
629-634
EN
Positron annihilation lifetime spectroscopy is accepted now as a method for the studies of elementary free volumes (free volume holes) in solids, in polymers in particular. The aim of this paper is to discuss some problems, the difficulties on the way of this application and to illustrate them by several examples obtained by the authors.
7
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Local Rigidity as a Criterion of Gas Permeation of Polymer and Composition Materials; PAL and TSL Experiments

33%
Shantarovich V., Gustov V., Belousova E., Polyakova A., Bekeshev V., Kevdina I., Yampolskii Y., Pastukhov A.
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vol. 125
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issue 3
806-811
EN
Various commercial and industrial properties of polymeric materials can be developed by the way of purposeful synthesis. For example, there are polymeric materials of extremely developed intrinsic microporosity. In attempts to further develop membrane properties (permeability and selectivity), the researchers artificially increase the pore sizes by various external influences, such as plastification by saturation of polymers with gases, sometimes in supercritical state, filling of a polymer with some non-organic components (zeolites). Sometimes, porosity of the composition appears to become higher than that of the components. This porosity, in difference with intrinsic one, can be called externally affected. The reason of these phenomena is not always clear, and in order to get some ideas in this field we suggest an experimental study using a combination of the two genetically interconnected (by spur processes) methods: positron annihilation lifetime spectroscopy and thermostimulated luminescence. This paper summarizes recently published and completely new results of the authors in order to illustrate the benefits of this experimental approach.
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