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Soft Matter and Biological Physics
Eur. Phys. J. E 3, 55-62 (2000)
DOI: 10.1007/PL00013677

Molecular mobility of sorbitol and maltitol: A $\chem{^{13}C}$ NMR and molecular dynamics approach

M.M. Margulies1, B. Sixou1, L. David1, G. Vigier1, R. Dolmazon2 and M. Albrand2

1  Groupe d'Etudes de Métallurgie Physique et de Physique des Matériaux, Institut National des Sciences Appliquées de Lyon, Bât. 502, 20 av. A. Einstein, 69621 Villeurbanne Cédex, France
2  Laboratoire de Chimie Organique, Institut National des Sciences Appliquées de Lyon, Bât. 403, 20 av. A. Einstein, 69621 Villeurbanne Cédex, France

Bruno.Sixou@insa-lyon.fr

(Received 4 October 1999 and Received in final form 27 December 1999)

Abstract
Molecular mobility in two similar organic glass formers, namely sorbitol and maltitol, is studied in order to understand their difference in the cross-over between $\alpha$ and $\beta$ relaxations, far above their respective glass transition temperatures. In this goal, the individual mobility of each carbon atom of the 6 carbon chain present both in sorbitol and maltitol is studied by means of $\chem{^{13}C}$ nuclear magnetic resonance and molecular dynamics simulations. Both techniques imply that the mobility of carbons located at the end of the 6 carbon chain is greater than that of any other carbon of this chain and that the difference in carbon mobility is greater within the sorbitol moiety of maltitol than in sorbitol. The relaxation time obtained by magnetic resonance for carbons at the end of the 6 carbon chain is related to the $\beta$ relaxation time and the one of carbons in the middle of the chain is in relation with the value of the $\alpha$ relaxation time. This result may suggest that the merging between the $\alpha$ and $\beta$ relaxation processes in both sugars would be related to the decrease of the differences in mobility between the atoms of 6 carbon chain.

PACS
87.15.Aa - Theory and modeling; computer simulation.
87.15.He - Dynamics and conformational changes.
76.60.Es - Relaxation effects.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2000