Local and global dynamics in the glass-forming di-isobutyl phthalate as studied by H NMR |
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Authors: | S Glowinkowski S Jurga W Suchanski E Szczesniak |
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Institution: | Institute of Physics A. Mickiewicz University, Ul. Umultowska 85, 61-614, Poznan, Poland |
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Abstract: | Spin-lattice relaxation times T1 and T1ρ as well as 1H NMR spectra have been employed to study the dynamics of the glass-forming di-isobutyl phthalate in the temperature range extending from 100 K, through the glass transition temperature Tg, up to 340 K. Below Tg NMR relaxation is governed by local dynamics and may be attributed to rotation of methyl groups at low temperatures and to motion of isobutyl groups in the intermediate temperature interval. Above Tg the main relaxation mechanism is provided by overall molecular motion. The observed relaxation behavior is explained by motional models assuming asymmetrical distributions of correlation times. The motional parameters obtained from Davidson-Cole distribution, which yields the best fit of the data at all temperatures are given. |
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Keywords: | NMR Relaxation times Molecular dynamics Distribution of correlation times |
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