Understanding the mechanism of cellulose dissolution in 1-butyl-3-methylimidazolium chloride ionic liquid via quantum chemistry calculations and molecular dynamics simulations
Understanding the mechanism of cellulose dissolution in 1-butyl-3-methylimidazolium chloride ionic liquid via quantum chemistry calculations and molecular dynamics simulations
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DOI：
10.1007/s10822-012-9559-9
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发表时间：
2012-03
影响因子：
3.5
通讯作者：
Hao Xu;Wenxiao Pan;Ruoxi Wang;Dongju Zhang;Chengbu Liu
中科院分区：
文献类型：
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作者：
Hao Xu;Wenxiao Pan;Ruoxi Wang;Dongju Zhang;Chengbu Liu
虽然N‘-二烷基咪唑离子液体(ILS)已被公认为纤维素溶解和加工的有效溶剂，但其在分子水平上的详细机理仍不清楚。在这项工作中，我们提出了一个量子化学和分子动力学相结合的模拟研究如何ILS溶解纤维素。在对溶解纤维素最有效的离子液体1-丁基-3-甲基咪唑氯的计算的基础上，我们进一步研究了纤维素模型(即聚合度n=2、4和6的纤维素齐聚物)在离子液体中的分子行为，包括结构特征和氢键模式。收集的数据表明，IL的氯离子和咪唑阳离子都通过氢键与齐聚物相互作用。然而，阴离子占据了齐聚物的第一配位壳层，并且阴离子与齐聚物之间的氢键强度和数目以及相互作用能远大于阳离子与齐聚物之间的相互作用能。结果表明，在阴阳离子的共同作用下，齐聚物中的分子内氢键被破坏。研究结果表明，氯离子在纤维素溶解过程中起着至关重要的作用，咪唑正离子对纤维素的溶解也有显著的贡献。这一观点不同于以往只强调氯离子在纤维素溶解中的重要性的观点。这些结果加深了我们对氯化咪唑离子液体中纤维素溶解的认识。
WhileN,N′-dialkylimidazolium ionic liquids (ILs) have been well-established as effective solvents for dissolution and processing of cellulose, the detailed mechanism at the molecular level still remains unclear. In this work, we present a combined quantum chemistry and molecular dynamics simulation study on how the ILs dissolve cellulose. On the basis of calculations on 1-butyl-3-methylimidazolium chloride, one of the most effective ILs dissolving cellulose, we further studied the molecular behavior of cellulose models (i.e. cellulose oligomers with degrees of polymerizationn= 2, 4, and 6) in the IL, including the structural features and hydrogen bonding patterns. The collected data indicate that both chloride anions and imidazolium cations of the IL interact with the oligomer via hydrogen bonds. However, the anions occupy the first coordination shell of the oligomer, and the strength and number of hydrogen bonds and the interaction energy between anions and the oligomer are much larger than those between cations and the oligomer. It is observed that the intramolecular hydrogen bond in the oligomer is broken under the combined effect of anions and cations. The present results emphasize that the chloride anions play a critically important role and the imidazolium cations also present a remarkable contribution in the cellulose dissolution. This point of view is different from previous one that only underlines the importance of the chloride anions in the cellulose dissolution. The present results improve our understanding for the cellulose dissolution in imidazolium chloride ILs.