Kovalov Kostiantyn M, Alekseev Olexander M, Lazarenko Maxim M, Zabashta Yu F, Grabovskii Yurii E, Tkachov Sergii Yu
Taras Shevchenko National University of Kyiv, Volodymyrska str. 64/13, Kyiv, 01601, Ukraine.
Nanoscale Res Lett. 2017 Dec;12(1):468. doi: 10.1186/s11671-017-2231-5. Epub 2017 Jul 26.
Influence of water in the different states on a structure and dielectric properties of microcrystalline cellulose were studied by of X-ray, thermogravimetry, and dielectric spectroscopy. At research of microcrystalline cellulose (MCC) with different content of water, it is shown that the molecules of water are located in the macropores of MCC and in multimolecular hydrated layers. It is shown that at the increase of concentration of water in a hydrated shell, the reorganization of molecules of cellulose in the surface of crystallites takes place, and as a result, their transversal size and crystallinity increase. It is shown that during the concentration of water, more than 13% in a continuous hydrated shell of crystallites appears. Temperature dependences of actual and imaginary parts of complex dielectric permittivity were studied in the interval of temperatures [-180 ÷ 120] °C on frequencies of f = 5, 10, 20, and 50 kHz. A low-temperature relaxation process and high-temperature transition were observed. Low-temperature relaxation process which is related to transition of surface methylol groups of molecules of cellulose conformation from tg to tt is shifted toward low temperatures at the increase of concentration of water in microcrystalline cellulose.
通过X射线、热重分析和介电谱研究了不同状态的水对微晶纤维素结构和介电性能的影响。在研究不同含水量的微晶纤维素（MCC）时发现，水分子位于MCC的大孔中以及多分子水合层中。研究表明，随着水合壳层中水浓度的增加，微晶表面的纤维素分子会发生重组，结果其横向尺寸和结晶度增加。研究表明，在微晶连续水合壳层中水的浓度超过13%时会出现这种情况。在温度区间[-180÷120]°C内，研究了复介电常数实部和虚部在f = 5、10、20和50 kHz频率下的温度依赖性。观察到了低温弛豫过程和高温转变。与纤维素分子构象的表面羟甲基基团从tg向tt转变相关的低温弛豫过程，会随着微晶纤维素中水浓度的增加而向低温方向移动。
