Dielectric and Photoluminescent Properties of the Water–Cellulose–NaCl Systems in a Wide Range of Temperatures: What is the Role of Ions?

Abstract

We have conducted a study of electric and spectral properties of the water–nanocellulose and water–nanocellulose–NaCl systems with different content of nanocellulose using dielectric and optical spectroscopy methods. We have demonstrated that the systems in which the content of nanocellulose was 0.08, 0.15, 0.3 and 0.6% undergo dielectric relaxation in the temperature range from –100 to 0 °C, whose nature is different from that of the pure water and explained by the dipole thermal polarization. The relaxation processes in both the water–nanocellulose and water–nanocellulose–NaCl systems were found to be due to the interaction between the surface layers of the cellulose nanocrystals and a hydration shell. The ions of Na+ and Cl− were found to distribute along the nanocellulose–ice interface and to partially block the formation of the hydrations shell around the nanocrystals of nanocellulose. Consequently, these ions were found to reduce the intensity of the dielectric relaxation process in the surface shells of the nanocellulose surrounded by a hydration shell.