Chen Qinghui, Chen Yehong, Wu Chaojun
State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, Shandong, China.
State Key Laboratory of Biobased Material and Green Papermaking, Qilu University of Technology (Shandong Academy of Sciences), Jinan 250353, Shandong, China.
Int J Biol Macromol. 2023 Apr 15;234:123694. doi: 10.1016/j.ijbiomac.2023.123694. Epub 2023 Feb 17.
Complex interactions between cellulose molecules and small molecules in Deep Eutectic Solvent (DES) systems can lead to dramatic changes in the structure of the hydrogen bond network in cellulose. However, the mechanism of interaction between cellulose and solvent molecules and the mechanism of evolution of hydrogen bond network are still unclear. In this study, cellulose nanofibrils (CNFs) were treated with DESs based on oxalic acid as hydrogen bond donors (HBD), and choline chloride, betaine, and N-methylmorpholine-N-oxide (NMMO) as hydrogen bond acceptors (HBA). The changes in the properties and microstructure of CNFs during treatment with the three types of solvents were investigated by Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The results showed that the crystal structures of CNFs were not changed during the process, but the hydrogen bond network evolved, increasing the crystallinity and crystallite size. Further analysis of the fitted peaks of FTIR and generalized two-dimensional correlation spectra (2DCOS) revealed that all three hydrogen bonds were disrupted to different degrees, the relative content changed, and evolved strictly in a certain order. These findings indicate that the evolution of hydrogen bond networks in nanocellulose has certain regularity.
在深共熔溶剂（DES）体系中，纤维素分子与小分子之间的复杂相互作用会导致纤维素中氢键网络结构发生显著变化。然而，纤维素与溶剂分子之间的相互作用机制以及氢键网络的演化机制仍不明确。在本研究中，以草酸作为氢键供体（HBD），氯化胆碱、甜菜碱和N-甲基氧化吗啉（NMMO）作为氢键受体（HBA），对纤维素纳米原纤（CNF）进行了DES处理。通过傅里叶变换红外光谱（FTIR）和X射线衍射（XRD）研究了三种类型溶剂处理过程中CNF的性能和微观结构变化。结果表明，在此过程中CNF的晶体结构未发生变化，但氢键网络发生了演化，结晶度和微晶尺寸增加。对FTIR拟合峰和广义二维相关光谱（2DCOS）的进一步分析表明，所有三种氢键均受到不同程度的破坏，相对含量发生变化，且严格按照一定顺序演化。这些发现表明，纳米纤维素中氢键网络的演化具有一定规律性。
