Onoda-Yamamuro Noriko, Inamura Yasuhiro, Yamamuro Osamu
Department of Natural Sciences, School of Science and Engineering, Tokyo Denki University, Hiki-gun, Saitama 350-0394, Japan.
Neutron Science Laboratory, Institute for Solid State Physics, University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
Gels. 2023 Nov 6;9(11):879. doi: 10.3390/gels9110879.
The dynamics of water and agarose molecules in an agarose aqueous solution has been studied by means of quasielastic neutron scattering (QENS). The dynamic structure factor (,) of the agarose aqueous solution was fitted well to the sum of the Lorentz and delta function. The former is attributed to the diffusive motion of water molecules and the latter to the local vibrational motion of agarose molecules. The self-diffusion coefficient of water molecules was obtained from the -dependence of the width of the Lorentz function, while the mean square displacement <> of agarose molecules was obtained from the -dependence of the intensity of the delta term. In the cooling direction, both and <> decreased with decreasing temperature and showed discontinuous changes around the thermal gelation temperature (around 314 K). In the heating direction, however, and <> did not show the obvious change below 343 K, indicating a large hysteresis effect. The present results of <> and revealed that the thermal gelation suppresses the motion of the polymer and accelerates the diffusion of water molecules. The activation energy of the diffusion of water in the sol state is the same as that of bulk water, but the in the gel state is clearly smaller than that of bulk water.
通过准弹性中子散射（QENS）研究了琼脂糖水溶液中水和琼脂糖分子的动力学。琼脂糖水溶液的动态结构因子S(Q,ω)与洛伦兹函数和δ函数之和拟合良好。前者归因于水分子的扩散运动，后者归因于琼脂糖分子的局部振动运动。水分子的自扩散系数D由洛伦兹函数宽度的Q依赖性获得，而琼脂糖分子的均方位移<u²>由δ项强度的Q依赖性获得。在冷却方向上，D和<u²>均随温度降低而减小，并在热凝胶化温度（约314 K）附近出现不连续变化。然而，在加热方向上，D和<u²>在343 K以下没有明显变化，表明存在较大的滞后效应。目前关于<u²>和D的结果表明，热凝胶化抑制了聚合物的运动并加速了水分子的扩散。溶胶状态下水扩散的活化能Ea与本体水相同，但凝胶状态下的Ea明显小于本体水。
