Dynamical Behaviour of Small Molecules Clathrated in Syndiotactic Polystyrene : a Solid State Deuterium NMR Investigation
The crystalline regions of the δ-form of syndiotactic polystyrene (s-PS) contain cavities in which certain small molecules can be absorbed. The mobility of six perdeuterated molecules: benzene, toluene, chloroform dichloromethane, 1,2-dichloroethane and 1,2-dibromoethane, present as a guest in these cavities, has been investigated via 2H NMR spectroscopy. For all samples the motional behavior of the molecules absorbed in the amorphous phase of the polymer differs from that shown by the molecules clathrated in the crystalline phase. The motion of all six molecules in the amorphous phase is approximately isotropic at a temperature T = 298 K or higher, but severely anisotropic when the molecules are included in the crystalline phase. The dynamical behavior of each solvent hosted in the crystalline phase of s-PS has been investigated by comparing spectra obtained by simulation of the effect of a certain molecular rotation on the 2H spectra with the experimental spectra.