Eur. Phys. J. E (2003) 12: 43-46
https://doi.org/10.1140/epjed/e2003-01-011-7

Methyl group dynamics in a confined glass

¹ Laboratoire des Verres, CNRS-UMR 5587, Université de Montpellier II, Bâtiment 13, 34095 Montpellier, France
² Dpto. Física de Materiales UPV/EHU, Apdo. 1072, 20080 San Sebastián, Spain
³ Unidad de Física de Materiales (CSIC-UPV/EHU), Apdo. 1072, 20080 San Sebastián, Spain
⁴ Donostia International Physics Center, Apdo. 1072, 20080 San Sebastián, Spain
⁵ Laboratoire de Chimie Physique, CNRS-UMR 8000, Bâtiment 349, Université de Paris-Sud, 91405 Orsay, France
⁶ Permanent adress: Groupe Mati`ere Condens´ee et Mat´eriaux, CNRS-UMR 6626, Bˆatiment 11A, Université de Rennes I, 35042 Rennes, France, France
⁷ Institute Laue Langevin, BP 156X, 38042 Grenoble, France

^* e-mail: moreno@ldv.univ-montp2.fr

Received: 1 January 2003
Published online: 5 November 2003

Abstract

We present a neutron scattering investigation on methyl group dynamics in glassy toluene confined in mesoporous silicates of different pore sizes. The experimental results have been analysed in terms of a barrier distribution model, such a distribution following from the structural disorder in the glassy state. Confinement results in a strong decreasing of the average rotational barrier in comparison to the bulk state. We have roughly separated the distribution for the confined state in a bulk-like and a surface-like contribution, corresponding to rotors at a distance from the pore wall respectively larger and smaller than the spatial range of the interactions which contribute to the rotational potential for the methyl groups. We have estimated a distance of 7 Å as a lower limit of the interaction range, beyond the typical nearest-neighbour distance between centers-of-mass (4.7 Å).