Study on the interaction between urea and cellulose by combining solid-state 13C CP/MAS NMR and extended Hückel charges

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• 作者：Jianhui Song (1)
  Hao Ge (1)
  Min Xu (1)
  Qun Chen (1)
  Lina Zhang (2)
  
• 关键词：Cellulose ; Aqueous NaOH/urea solvent ; Interaction ; 13C CP/MAS NMR ; Extended Hückel charges
• 刊名：Cellulose
• 出版年：2014
• 出版时间：December 2014
• 年：2014
• 卷：21
• 期：6
• 页码：4019-4027
• 全文大小：2,254 KB
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• 作者单位：Jianhui Song (1)
  Hao Ge (1)
  Min Xu (1)
  Qun Chen (1)
  Lina Zhang (2)
  
  1. Physics Department and Shanghai Key Laboratory of Magnetic Resonance, East China Normal University, 3663 North Zhongshan Road, Shanghai, 200062, People’s Republic of China
  2. Department of Chemistry, Wuhan University, Wuhan, 430072, People’s Republic of China
  
• ISSN：1572-882X

文摘

In this article, solid-state 13C CP/MAS NMR combined with extended Hückel charges was applied to investigate the interaction between urea and cellulose in the NaOH/urea aqueous solvent system. Direct experimental evidence was provided to support the interaction between urea and cellulose. The solid-state 13C CP/MAS NMR results revealed that complicated complexes are formed by urea, NaOH and cellulose in the solution. Excess urea exists in a free state, which explains why 7?wt% NaOH/12?wt% urea/81?wt% H2O is the optimal ratio selection to dissolve cellulose. Based on the correlation in which the computed extended Hückel charge on carbon of urea is approximately inversely proportional to its 13C chemical shift, a possible interaction model of cellulose, NaOH and urea was proposed. Interactions exist between any two of urea, NaOH and cellulose, which results in the cellulose chain being surrounded by NaOH and urea molecules. NaOH and urea may be in the same surface layer of cellulose chains.