¹³C NMR relaxation of iso-poly(2-vinylpyridinium chloride) in aqueous solution. Effects of electrostatic interactions on local chain dynamics

Measurements of ¹³C spin-lattice relaxation times, T₁, and nuclear Overhauser effects, NOE, were carried out as a function of temperature at two magnetic fields for iso-poly(2-vinylpyridine) (iso-P2VP) in 1,4-dioxane-d₈ and iso-poly(2-vinylpyridinium chloride) (iso-P2VPCl), in D₂O to investigate the effects of electrostatic interactions on local chain dynamics. For main chain carbons of both polymers, the experimental T₁ and NOE data are in good agreement with the Dejean-Laupretre-Monnerie (DLM) model in the entire temperature range. It was found that the local conformational transitions of main chain and the libration are more restricted for iso-P2VPCl than iso-P2VP. For pyridyl ring carbons, the experimental data were reproduced by the models combining the DLM model and restricted ring rotations. The angular amplitude α of ring rotation of iso-P2VPCl is smaller than that of iso-P2VP. These results imply that both local motions of main chain and side chain are affected by the electrostatic interactions.