Physico-Chemical nanomaterials science

Electrical properties of water-nanocellulose systems in a wide temperature range.

D.O. Shevtsov1, M.M. Lazarenko1, О.М. Alekseev1, S.A. Alekseev1, V.A.Barbash 2, K.S. Yablochkova1, V.I. Kovalchuk1, S.G. Nedilko1, M.V. Lazarenko3

1 Taras Shevchenko National University of Kyiv, Physical Faculty, Volodymyrs’ka St. 64/13, Kyiv 01601, Ukraine.
E-mail: shevadima15z@gmail.com
2 National Technical University of Ukraine “Igor Sikorsky Kyiv Polytechnic Institute”, prospect Peremogy 37, Kyiv, Ukraine 
3National University of Food Technologies, Volodymyrs’ka St. 68, Kyiv-01601, Ukraine.

	The lyotropic liquid-crystalline phases in water suspensions of cellulose nanocrystals have received much attention, leading to the extensive research of their liquid state rheological, optical, and structural properties. However, few researchers have studied the physical, and, in particular, electrical, properties of water-nanocellulose systems in the solid state. Moreover, existing data mainly concerns the nanocellulose films with low water concentrations.
	An essential feature of the solid nanocellulose-water system structure is the spatial heterogeneity of its nanocrystals, which arises when samples are prepared by evaporation or freezing. At different technological stages of the sample formation, ionic impurities concentrate in inter-crystalline layers of ice or cellulose nanocrystals. Furthermore, the interface regions of nanocrystals (in the polycrystals or agglomerates they form) contain various structural defects. As nano-scale spatial inhomogeneities and structural defects can significantly affect phase transitions and relaxation processes, the study of the physical properties of water-nanocellulose systems in the temperature region near the phase transition constitutes a significant interest. 
	 Our present work discusses the properties of the nanocellulose systems with different water concentrations studied by thermogravimetric analysis, IR spectroscopy, and dielectric spectroscopy methods. We report that a dielectric relaxation is observed in nanocellulose-water systems in the temperature range of [–100¸ 0] оС, and that nature of this process differs from the dielectric relaxation in ice. 
	The relaxation process in nanocellulose solutions can be attributed to the surface layers of cellulose nanocrystals, which are surrounded by a hydrate shell. The mechanism of the relaxation process can be explained by the conformational motion of methylol groups on the surface these nanocellulose crystals.