Lattice Defects in Plastic Organic Solids 9. Nuclear Magnetic Resonance Studies of Translational Molecular Motion in Solids of Intermediate Entropies of Fusion

Abstract Studies have been made of the effects of temperature and sample purity on the c.w., NMR line narrowing behaviour at high temperatures for the following rotator phase organic solids of intermediate entropies of fusion: perfluorocyclohexane, triethylenediamine, 2-bromo-2, 3, 3′-trimethylbutane, 2-chloro-2,3,3′-trimethylbutane, 2,3-dibromo-2,3-dimethylbutane and tetra-(fluoromethyl)-methane. The evaluated correlation times and activation energies for the solids of high entropy of fusion are equivalent to those for self-diffusion as measured by the radiotracer (or plastic deformation) technique. Proceeding to lower entropies of fusion there is a gradually increasing divergence between the two sets of data. It is proposed that this variation is a consequence of the way in which the different techniques reflect translational motion in systems with increasing defect disorder.