Investigation of dynamical properties of free water in hydroxypropyl cellulose–water mixture by PFG-NMR

The dynamical behavior of water molecules in hydroxypropyl cellulose (HPC)–water mixtures was observed by the pulse field gradient (PFG) NMR method. For a decay curve of the spin-echo signal intensity of a water proton peak, a contribution of the diffusional motion of free water is observed. The water content dependence of the NMR relaxation time and diffusion coefficient of free water shows characteristic behavior reflecting the isotropic-cholesteric phase transition of HPC. These parameters of free water obtained by PFG-NMR correlate strongly with the fast dynamics of free water observed in the GHz region, and this correlation is explained by dynamics of water constrained by the geometrical self-similarity formed by the HPC molecules.