Intermolecular Interactions and 3D Structure in Cellulose鈥揘aOH鈥揢rea Aqueous System

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• 作者：Zhiwei Jiang ; Yan Fang ; Junfeng Xiang ; Yanping Ma ; Ang Lu ; Hongliang Kang ; Yong Huang ; Hongxia Guo ; Ruigang Liu ; Lina Zhang
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：August 28, 2014
• 年：2014
• 卷：118
• 期：34
• 页码：10250-10257
• 全文大小：414K
• ISSN：1520-5207

文摘

The dissolution of cellulose in NaOH/urea aqueous solution at low temperature is a key finding in cellulose science and technology. In this paper, ¹⁵N and ²³Na NMR experiments were carried out to clarify the intermolecular interactions in cellulose/NaOH/urea aqueous solution. It was found that there are direct interactions between OH^{鈥?/sup> anions and amino groups of urea through hydrogen bonds and no direct interaction between urea and cellulose. Moreover, Na+ ions can interact with both cellulose and urea in an aqueous system. These interactions lead to the formation of cellulose鈥揘aOH鈥搖rea鈥揌₂O inclusion complexes (ICs). 23Na relaxation results confirmed that the formation of urea鈥揙H鈥?/sup> clusters can effectively enhance the stability of Na+ ions that attracted to cellulose chains. Low temperature can enhance the hydrogen bonding interaction between OH鈥?/sup> ions and urea and improve the binding ability of the NaOH/urea/H₂O clusters that attached to cellulose chains. Cryo-TEM observation confirmed the formation of cellulose鈥揘aOH鈥搖rea鈥揌₂O ICs, which is in extended conformation with mean diameter of about 3.6 nm and mean length of about 300 nm. Possible 3D structure of the ICs was proposed by the M06-2X/6-31+G(d) theoretical calculation, revealing the O3H路路路O5 intramolecular hydrogen bonds could remain in the ICs. This work clarified the interactions in cellulose/NaOH/urea aqueous solution and the 3D structure of the cellulose chain in dilute cellulose/NaOH/urea aqueous solution.}