Dynamics and thermodynamics of water in PAMAM dendrimers at subnanosecond time scales

The dynamic and thermodynamic properties of the water in polyamidoamine (PAMAM) dendrimers at subnanosecond time scales at three pH values were studied. The three pH values include high pH with none of the primary or tertiary amines protonated, intermediate pH with only the primary amines protonated and low pH with all amines protonated. It was shown that translational and rotational dynamics of water are affected by the PAMAM-water interactions as well as due to the confinement in the interior of the dendrimer. It was found that the reduction of translational or rotational diffusion is accompanied by a blue shift of the corresponding libration motions, indicating higher local force constants for these motions.