An ESR study on gamma-irradiated poly(vinyl alcohol)

Zainuddin, Z., Hill, D. J. T. and Le, T. T. (2001) An ESR study on gamma-irradiated poly(vinyl alcohol). Radiation Physics And Chemistry, 62 2-3: 283-291. doi:10.1016/S0969-806X(01)00188-8

Author Zainuddin, Z.
Hill, D. J. T.
Le, T. T.
Title An ESR study on gamma-irradiated poly(vinyl alcohol)
Journal name Radiation Physics And Chemistry   Check publisher's open access policy
ISSN 0969-806X
Publication date 2001
Sub-type Article (original research)
DOI 10.1016/S0969-806X(01)00188-8
Volume 62
Issue 2-3
Start page 283
End page 291
Total pages 9
Place of publication Oxford, UK
Publisher Pergamon
Collection year 2001
Language eng
Subject C1
250599 Macromolecular Chemistry not elsewhere classified
780102 Physical sciences
Abstract The formation of radicals in poly(vinyl alcohol), PVA, powder irradiated at 77 K by gamma -rays and the transformations of these radicals during photolysis with visible wavelengths and on thermal annealing have been studied. After irradiation a four-line ESR spectrum was observed. It was assigned to a triplet of the C-alpha-radical (38%), with a splitting of 3.27 mT, superimposed on a doublet (62%) with a splitting of 2.7 mT. The doublet appears to be composed of two radicals, one of which is photo-bleachable (58%) and the other which is not photo-bleachable (42%). This suggests that the latter radical is a neutral radical. The photo-bleachable component of the doublet has been assigned to a carbonyl anion radical. but the second doublet due to a neutral radical is unassigned. The total G-value for formation of radicals at 77 K was found to be 2.41 +/- 0.03. Upon illumination with visible light, the anion radicals were removed and the doublet components or the spectrum diminished in intensity, while the three-line spectrum of the C-alpha-radical became more clearly visible. This transition was due to the photo-detachment of electrons from traps which were proposed to be located on carbonyl groups in the polymer resulting from incomplete hydrolysis of the vinyl acetate. The photo-decay of the anion radicals could be satisfactorily described by a two-stage process. The first stage comprised the decay of approximately 80% of the anion radicals present, while the second stage was associated with the decay of the remaining 20%. Subsequent thermal annealing of a photolysed sample to 290 K led to a change in the shape of the spectrum to form a more clearly defined triplet, As the doublet of the neutral radical decays on thermal annealing between 150 and 250K, the C-alpha-radical is formed. (C) 2001 Elsevier Science Ltd. All rights reserved.
Keyword Chemistry, Physical
Nuclear Science & Technology
Physics, Atomic, Molecular & Chemical
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collection: School of Chemistry and Molecular Biosciences
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Created: Tue, 14 Aug 2007, 15:28:31 EST