<br>阐明低温低浓度 NaOH 溶液中纤维素 I 到 II 晶体转变过程中纤维素分子的结构变化和 Na 离子动力学,Carbohydrate Polymers

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阐明低温低浓度 NaOH 溶液中纤维素 I 到 II 晶体转变过程中纤维素分子的结构变化和 Na 离子动力学
Carbohydrate Polymers ( IF 10.7 ) Pub Date : 2024-02-03 , DOI: 10.1016/j.carbpol.2024.121907
Yuki Kugo ₁ , Satoshi Nomura ₁ , Takuya Isono ₂ , Shin-Ichiro Sato ₂ , Masashi Fujiwara ₂ , Toshifumi Satoh ₃ , Hirofumi Tani ₂ , Tomoki Erata ₂ , Kenji Tajima ₂

Affiliation

低温低浓度碱处理有利于纤维素I向II的晶型转变。然而，过渡机制仍不清楚。因此，在本研究中，我们使用原位固态 C CP/MAS NMR、WAXS 和 Na NMR 弛豫测量来追踪转变。原位固态 C CP/MAS NMR 和 WAXS 测量表明，低温下将纤维素浸泡在 NaOH 中会破坏分子内氢键并降低纤维素的结晶度。钠离子 (NaOH) 的动力学在引起这些现象中起着至关重要的作用。 Na NMR 弛豫测量表明，Na 离子关联时间在晶体转变过程中变得更长。这种转变需要钠离子 (NaOH) 渗透到纤维素晶体中并降低钠离子迁移率，这在低温或高 NaOH 浓度下发生。纤维素和 NaOH 之间的相互作用破坏分子内氢键，诱导纤维素分子构象变化，形成更稳定的排列。这削弱了纤维素的疏水相互作用，有利于NaOH和水渗透到晶体中，导致碱纤维素的形成。我们的研究结果表明，控制 NaOH 动力学的策略可能会导致纤维素 II 的新型制备方法的发现。

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Elucidating the structural changes of cellulose molecules and dynamics of Na ions during the crystal transition from cellulose I to II in low temperature and low concentration NaOH solution

Low-concentration alkali treatments at low temperatures facilitate the crystal transition of cellulose I to II. However, the transition mechanism remains unclear. Hence, in this study, we traced the transition using in situ solid-state C CP/MAS NMR, WAXS, and Na NMR relaxation measurements. In situ solid-state C CP/MAS NMR and WAXS measurements revealed that soaking cellulose in NaOH at low temperatures disrupts the intramolecular hydrogen bonds and lowers the crystallinity of cellulose. The dynamics of Na ions (NaOH) play a crucial role in causing these phenomena. Na NMR relaxation measurements indicated that the Na-ion correlation time becomes longer during the crystal transition. This transition requires the penetration of Na ions (NaOH) into the cellulose crystal and a reduction in Na-ion mobility, which occurs at low temperatures or high NaOH concentrations. The interactions between cellulose and NaOH disrupt intramolecular hydrogen bonds, inducing a conformational change in the cellulose molecules into a more stable arrangement. This weakens the hydrophobic interactions of cellulose, and facilitates the penetration of NaOH and water into the crystal, leading to the formation of alkali cellulose. Our findings suggest that a strategy to control NaOH dynamics could lead to the discovery of a novel preparation method for cellulose II.

更新日期：2024-02-03

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