Dynamics NMR investigations of a glassy crystal confined in porous materials

The temperature dependence of the proton relaxation rates has been studied in molecular glassy crystals cyano-adamantane (C10H15CN) confined in the porous space of a silica glass of 60 Angstrom and 150 Angstrom nominal pore sizes. In the temperature range corresponding to the hulk plastic phase, the NMR proton lineshape of the confined materials revealed a two phase system consisting of a liquid-like component and a crystalline solid bulk-like component. As for the bulk, the alpha process, related to the dipolar axis motion, controlled both T-1z and T-1 rho in the largest pores. From, the NMR results we concluded that the dynamics of this alpha-relaxation process is slightly enhanced by the confinement giving rise to a negative shift of the glass transition temperature. On the contrary the confinement has no influence on the relaxation rates in the glassy state.