¹³C NMR relaxation of poly(acrylic acid) in aqueous solution. Effects of charge density on local chain dynamics

Spin-lattice relaxation time and nuclear Overhauser effect of polyacrylic acid with different degree of neutralization at two magnetic fields were measured as a function of temperature. The main chains were analyzed by Dejean-Laupretre-Monnerie (DLM) model to study the effects of charge density on the local chain dynamics. The activation energy, E*, associated with a potential barrier for conformational transition was examined. E* was evaluated by subtracting the activation energy of solvent viscosity from the apparent activation energy. The mechanisms of local motion as reflected in the correlation function were independent of temperature.