NUCLEAR-SPIN-LATTICE RELAXATION IN TRANS-POLYACETYLENE (CH)X - A CONFINED SOLITON MODEL INCLUDING NUCLEAR-SPIN FLIP DIFFUSION

A 'confined soliton model' in which the solitons move over a small part of the chain is developed. The on-chain nuclei are relaxed directly by contact hyperfine interactions while the remainder nuclei relax via nuclear spin flip diffusion. It is found that the proton spin-lattice relaxation data can be rationalized in terms of the fast and confined one-dimensional hopping motion of the soliton whilst that for enriched **1**3C one requires in addition a much more dominating mechanism that of nuclear spin flip diffusion.