Impact of Hydrophilic Surfaces on Interfacial Water Dynamics Probed with NMR Spectroscopy

In suspensions of Nafion beads and of cationic gel beads, NMR spectroscopy showed two water-proton resonances, one representing intimate water layers next to the polymer surface, the other corresponding to water lying beyond. Both resonances show notably shorter spin lattice relaxation times (T1) and smaller self-diffusion coefficients (D) indicating slower dynamics than bulk water. These findings confirm the existence of highly restricted water layers adsorbed onto hydrophilic surfaces and dynamically stable water beyond the first hydration layers. Thus, aqueous regions on the order of micrometers are dynamically different from bulk water.