Traveling Defects in 1,4-trans-Polybutadiene as an Inclusion Complex in Perhydrotriphenylene Canals and a Comparison with Molecular Motions in the Crystalline Solid State.

1,4-trans-Polybutadiene in perhydrotriphenylene (PHTP) canals provides a model system for studying the behavior of a single polymer molecule in a highly hydrophobic environment. Solid state deuterium NMR spectroscopy was used to obtain explicit molecular level information about the motions of 1,4-trans- 1,1,4,4-d sub 4-polybutadiene in the polybutadiene - PHTP complex. These results were compared to the mobility of deuterated polybutadiene when the PHTP matrix had been removed, and to the mobility of recrystallized polybutadiene in the solid state. The isolated molecules of deuterated 1,4-trans- polybutadiene in PHTP canals undergo rapid (tau sub c = 10 sup -7 s) diffusional motions about the long axis of the polymer chain. These motions are consistent with a traveling defect or soliton that produces rapid and complete conformational averaging of the C-D bond vector about a cylindrical axis. These motions are not completely frozen out ( tau sub c = 10 sup -3 s) even at -160C, suggesting that the hydrophobic canals of the PHTP molecules provide a highly unusual environment for polybutadiene. In contrast, when the PHTP matrix is removed the deuterated polybutadiene demonstrates motional properties that are very similar to those of recrystallized polybutadiene. At ambient temperature (i. e., Form I) the crystalline regions are static on the deuterium NMR timescale, whereas the amorphous connections between these regions undergo rapid (tau sub c = 10 sup -7 s) tetrahedral jumps. Above the Form I - Form II solid-solid transition but below the melt temperature, the chains in the crystalline regions of this material undergo the rapid diffusional motions observed for polybutadiene in the PHTP canals. These results show that polybutadiene in PHTP canals is similar to Form II material, but that the solid-solid transition to Form I is prohibited by the canals.