PRESSURE-DEPENDENCE OF THE DYNAMICS OF AN ORGANIC INCLUSION COMPOUND INVESTIGATED BY INCOHERENT QUASI-ELASTIC NEUTRON-SCATTERING

The nitroxide C9H16NO2 (referred to as tano) forms channel inclusion c ompounds with linear hydrocarbons. At room temperature, both tano and chain molecules are dynamically disordered. When the temperature is de creased, one phase transition is observed. The pressure dependence of the temperature of transition and the evolution of the individual moti ons have been studied by incoherent quasielastic neutron scattering in the case of a tano-octane system. The transition temperature increase s with the pressure with a slope (dT(t)/dP)(P=0) = 24 K kbar(-1). The transition mechanism is connected to the lock-in of both tano (interco nversion) and chain (reorientation) molecules, as a result of strong c orrelations between host and guest substructures. A residual disorder persists in the low-temperature phase confirming that all the tano mol ecules are not dynamically equivalent.