Temperature dependence of ESR spectra of nitroxide spin probe in glassy polymers

Temperature dependencies of ESR spectra of nitroxide spin probes in glassy polymers near and below glass transition temperature were examined in detail. Three temperature ranges, each characterized by specific changes in spectral shape, were defined. (i) In the low temperature range, ESR spectra of...

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Bibliographic Details
Published in:Journal of polymer science. Part B, Polymer physics Polymer physics, 2009-03, Vol.47 (6), p.563-575
Main Authors: Chernova, Daria A, Vorobiev, Andrey Kh
Format: Article
Language:English
Subjects:
additives
amorphous
ESR/EPR
glassy polymers
molecular dynamics
molecular mobility
nitroxides
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Summary:Temperature dependencies of ESR spectra of nitroxide spin probes in glassy polymers near and below glass transition temperature were examined in detail. Three temperature ranges, each characterized by specific changes in spectral shape, were defined. (i) In the low temperature range, ESR spectra of nitroxide radical in glassy polymer matrix weakly depend on temperature and remain qualitatively the same. (ii) In the intermediate temperature range, significant changes in the shape of spectra are observed. (iii) A new phenomenon was revealed near and below glass transition temperature: narrowing of linewidths occurs while the ratio of amplitudes of different components varies insignificantly. Analysis of molecular rotational mobility was carried out by means of commonly used empirical approaches. It was shown that widely used formulas and empirical approaches are not applicable for characterization of molecular mobility in glassy polymers. Mechanisms of rotational molecular movements in glassy polymers are discussed.
ISSN:0887-6266
1099-0488
DOI:10.1002/polb.21662