Dynamics NMR investigations of a glassy crystal confined in porous materials

Abstract
The temperature dependence of the proton relaxation rates has ben studied in molecular glassy crystals cyano-adamantane (C₁₀H₁₅CN) confined in the porous space of a silica glass of 60Å and 150Å nominal pore sizes. In the temperature range corresponding to the bulk 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 [Math] process, related to the dipolar axis motion, controlled both T_1z and T_1p in the largest pores. From the NMR results we concluded that the dynamics of this [Math]-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.