Trehalose is chosen as a model molecule to investigate the dissolution mechanism of cellulose in NaOH/urea aqueous solution. The combination of neutron total scattering and empirical potential structure refinement yields the most probable all-atom positions in the complex fluid and reveals the cooperative dynamic effects of NaOH, urea, and water molecules in the dissolution process. NaOH directly interacts with glucose rings by breaking the inter- and intra-molecular hydrogen bonding. Na⁺, thus, accumulates around electronegative oxygen atoms in the hydration shell of trehalose. Its local concentration is thereby 2–9 times higher than that in the bulk fluid. Urea molecules are too large to interpenetrate into trehalose and too complex to form hydrogen bonds with trehalose. They can only participate in the formation of the hydration shell around trehalose via Na⁺ bridging. As the main component in the complex fluid, water molecules have a disturbed tetrahedral structure in the presence of NaOH and urea. The structure of the mixed solvent does not change when it is cooled to −12 °C. This indicates that the dissolution may be a dynamic process, i.e., a competition between hydration shell formation and inter-molecule hydrogen bonding determines its dissolution. We, therefore, predict that alkali with smaller ions, such as LiOH, has better solubility for cellulose.

中文翻译：

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海藻糖在NaOH/尿素水溶液中溶解机理的中子全散射研究

选择海藻糖作为模型分子研究纤维素在NaOH/尿素水溶液中的溶解机理。中子全散射和经验势结构细化的结合产生了复杂流体中最可能的全原子位置，并揭示了 NaOH、尿素和水分子在溶解过程中的协同动态效应。NaOH 通过破坏分子间和分子内氢键直接与葡萄糖环相互作用。因此， Na ⁺聚集在海藻糖水合壳中带负电的氧原子周围。因此，其局部浓度比本体流体中的浓度高 2-9 倍。尿素分子太大而无法与海藻糖相互渗透，并且太复杂而无法与海藻糖形成氢键。^{它们只能通过Na +}桥接参与海藻糖周围水合壳的形成。作为复杂流体的主要成分，水分子在NaOH和尿素存在下具有扰乱的四面体结构。混合溶剂冷却至-12℃时结构不发生变化。这表明溶解可能是一个动态过程，即水化壳的形成和分子间氢键之间的竞争决定了其溶解。因此，我们预测离子较小的碱（例如 LiOH）对纤维素具有更好的溶解度。