Dissolution mechanism of cellulose in a solution of aqueous sodium hydroxide revealed by molecular dynamics simulations
Dissolution mechanism of cellulose in a solution of aqueous sodium hydroxide revealed by molecular dynamics simulations
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DOI：
10.3183/npprj-2015-30-01-p067-077
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发表时间：
2015
影响因子：
1.2
通讯作者：
H. Miyamoto;U. Schnupf;K. Ueda;C. Yamane
中科院分区：
文献类型：
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作者：
H. Miyamoto;U. Schnupf;K. Ueda;C. Yamane
为了解释纤维素的溶解状态，采用分子动力学模拟方法研究了纤维二糖在不同浓度和温度的氢氧化钠水溶液中的溶解行为。在263 K下，8重量%的氢氧化钠溶液对于在氢氧化钠水溶液介质中溶解纤维素是必要的。在钠离子的等高线密度图中，在纤维二糖周围的特定位置观察到一些密度云。值得注意的是，在263 K和300 K下，在葡萄糖还原端的O2和O3之间的高钠离子密度区域存在于具有8wt%溶液的模型系统中。这表明，当还原端的HO3与非还原端的O5形成分子内氢键，而还原端的HO2与O1相互作用时，钠离子可能进入密度云。从长远来看，氢氧根离子几乎没有表现出与纤维二糖的直接相互作用。也就是说，接近纤维素的钠离子和纤维素周围的水结构最有可能在氢氧化钠溶液中溶解纤维素中起作用。提出了纤维素在8wt%氢氧化钠水溶液中低温溶解的机理。
The dissolution of cellobiose in aqueous solutions of sodium hydroxide at different concentrations and temperatures was characterized utilizing molecular dynamics simulations in order to explain the dissolution state of cellulose. A 8 wt% solution of sodium hydroxide at 263 K is essential to dissolve cellulose in aqueous sodium hydroxide medium. In the contour density maps of the sodium ions, a few density clouds were observed at specific positions around cellobiose. Notably, an area of high sodium ions density between O2 and O3 on the reducing-end of glucose existed in the model systems with 8 wt% solution modeled at 263 K and 300 K. This suggests that it is possible that sodium ions can access the density clouds when the HO3 of the reducing end forms an intramolecular hydrogen bond with the O5 of the nonreducing end, and the HO2 of the reducing end interacts with O1. In perspective, the hydroxide ions exhibited almost no direct interactions with cellobiose. That is, the sodium ions that approached cellulose and the water structure around cellulose most likely play a role in dissolving cellulose in a solution of sodium hydroxide. A dissolution mechanism of cellulose in an aqueous solution of 8 wt% sodium hydroxide at low temperatures is presented.