Cellulose Research Unit, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
Division of Natural Resources and Eco-materials, Graduate School of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwai-cho, Fuchu, Tokyo 183-8509, Japan.
Molecules. 2020 Oct 15;25(20):4726. doi: 10.3390/molecules25204726.
Hydroxyethyl cellulose (HeC) maintains high water solubility over a wide temperature range even in a high temperature region where other nonionic chemically modified cellulose ethers, such as methyl cellulose (MC) and hydroxypropylmethyl cellulose (HpMC), demonstrate cloud points. In order to clarify the reason for the high solubility of HeC, the temperature dependence of the hydration number per glucopyranose unit, , for the HeC samples was examined by using extremely high frequency dielectric spectrum measuring techniques up to 50 GHz over a temperature range from 10 to 70 °C. HeC samples with a molar substitution number () per glucopyranose unit by hydroxyethyl groups ranging from 1.3 to 3.6 were examined in this study. All HeC samples dissolve into water over the examined temperature range and did not show their cloud points. The value of for the HeC sample possessing the of 1.3 was 14 at 20 °C and decreased gently with increasing temperature and declined to 10 at 70 °C. The values of the HeC samples are substantially larger than the minimum critical value of ca. 5 necessary to be dissolved into water for cellulose ethers such as MC and HpMC, even in a high temperature range. Then, the HeC molecules possess water solubility over the wide temperature range. The temperature dependence of for the HeC samples and triethyleneglycol, which is a model compound for substitution groups of HeC, is gentle and they are similar to each other. This observation strongly suggests that the hydration/dehydration behavior of the HeC samples was essentially controlled by that of their substitution groups.
羟乙基纤维素（HeC）在很宽的温度范围内保持高水溶性，即使在其他非离子化学改性纤维素醚（如甲基纤维素（MC）和羟丙基甲基纤维素（HpMC））显示浊点的高温区域也是如此。为了阐明 HeC 高溶解度的原因，通过使用极其高频介电谱测量技术，在 10 至 70°C 的温度范围内，研究了每葡萄糖吡喃糖单元的水合数 随温度的变化关系，对于 HeC 样品，羟乙基基团的摩尔取代数（）为 1.3 至 3.6。在这项研究中，检查了每葡萄糖吡喃糖单元的摩尔取代数（）为 1.3 至 3.6 的 HeC 样品。所有 HeC 样品都在研究的温度范围内溶解在水中，并且没有显示出浊点。在 20°C 时，具有 1.3 的 的 HeC 样品的值为 14，随着温度的升高而逐渐降低，并在 70°C 时降至 10。HeC 样品的值明显大于 MC 和 HpMC 等纤维素醚溶解所需的临界 值约 5，即使在高温范围内也是如此。然后，HeC 分子在很宽的温度范围内具有水溶性。HeC 样品和三甘醇的 值随温度的变化关系很温和，它们彼此相似。这一观察结果强烈表明，HeC 样品的水合/去水合行为主要由其取代基的行为控制。
