title: Methyl group dynamics in a confined glass.
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 A as a lower limit of the interaction range, beyond the typical nearest-neighbour distance between centers-of-mass (4.7 A).
authors.affiliation: Laboratoire des Verres, CNRS-UMR 5587, Université de Montpellier II, Bâtiment 13, 34095 Montpellier, France. moreno@ldv.univ-montp2.fr
authors.forename: A J
authors.initials: AJ
authors.lastname: Moreno
authors.forename: J
authors.initials: J
authors.lastname: Colmenero
authors.forename: A
authors.initials: A
authors.lastname: Alegría
authors.forename: C
authors.initials: C
authors.lastname: Alba-Simionesco
authors.forename: G
authors.initials: G
authors.lastname: Dosseh
authors.forename: D
authors.initials: D
authors.lastname: Morineau
authors.forename: B
authors.initials: B
authors.lastname: Frick