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首页> 外文期刊>The journal of physical chemistry, B. Condensed matter, materials, surfaces, interfaces & biophysical >Theoretical Investigation of Dissolution and Decomposition Mechanisms of a Cellulose Fiber in Ionic Liquids
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Theoretical Investigation of Dissolution and Decomposition Mechanisms of a Cellulose Fiber in Ionic Liquids

机译：离子液体纤维素纤维溶解和分解机制的理论研究

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We carry out detailed computational investigations of the decomposition and dissolution processes of a cellulose I-beta fiber in the ionic liquid (IL) solvent, [C(2)MIm][OAc]. First, we investigated the properties of the interactions between cellulose chains in the cellulose fiber, including interchain H-bonds and stacking interactions, with the quantum and molecular mechanics (QM/MM) methods, employing a microscopic solvent model. From the calculation results, it is indicated that interchain interaction energies are largely influenced in the axial direction by the solvent effects of the IL and that the degree of interactions depends on the site of the glucose unit, compared to that in the equatorial (parallel) direction. To further investigate the impact of the IL on intrachain H-bonds and its relation to interchain interaction, we perform molecular dynamics (MD) simulations. Our results indicate that it is difficult to disrupt a strong three-dimensional H-bond network in the cellulose fiber at room temperature, even with ILs. On the other hand, the total number of H-bonds in the cellulose fiber continues to decrease from the beginning of the dissolution and decomposition processes in the IL at 400 K. The results indicate that the number of inter- and intrachain H-bonds reduces sequentially and that intrachain H-bond breakage inside the cellulose fiber proceeds prior to interchain H-bond disruption. Also, it is shown that the breakage of interchain H-bonds starts playing an important role in enhancing the separation of cellulose chains from each other. On the role of anions in the dissolution and decomposition processes of the cellulose fiber in the IL, our results indicate that the formation of H-bonds between [OAc](-) anions and a cellulose chain is facilitated by the intercalation of [OAc](-) anions into the cellulose fiber and that, in particular, the breakage of intrachain H-bonds in cellulose chains due to [OAc](-) anions proceeds prior to that of interchain H-bonds. On the role of cations, it is shown that [C(2)MIm](+) cations could interact with the cellulose and stabilize detached cellulose chains due to the stacking effect through the van der Waals interaction, in particular, within the first solvation shell of a cellulose chain in ILs. Our results suggest that the enhancement of the flexibility of rigid cellulose chains triggered by the breakage of intrachain H-bonds due to anions starts decomposition processes accompanied by dissolution processes due to the intercalation of cations, synergistically, and, then, both dissolution and decomposition processes are executed simultaneously.
机译：我们对离子液体（IL）溶剂中的纤维素I-β纤维的分解和溶解过程进行详细的计算研究，[C（2）MIM] [OAC]。首先，我们研究了纤维素纤维中纤维素链之间的相互作用的性质，包括间隙H键和堆叠相互作用，用量子和分子力学（QM / mm）方法，采用微观溶剂模型。从计算结果中，表明，通过IL的溶剂效应，交流相互作用能量在很大程度上影响轴向，并且相互作用程度取决于赤道（并联）的位置取决于葡萄糖单元的部位方向。为了进一步研究IL对内颈H键的影响及其与交互式相互作用的关系，我们执行分子动力学（MD）模拟。我们的结果表明，即使使用ILS，难以在室温下在纤维素纤维中扰乱强三维H键网络。另一方面，纤维素纤维中的H键的总数从IL的溶解和分解过程的开始持续下降，在400k中，结果表明，颈内部的H键的数量减少了顺序地并且在纤维素纤维内部内部的H键粘合断裂在间歇性H键破坏之前进行。而且，结果表明，在增强彼此的纤维素链的分离方面，在增强纤维素链的分离方面开始发挥重要作用。关于阴离子在IL中纤维素纤维溶出和分解过程中的作用，我们的结果表明，通过[OAC]的插入，促进了[OAC]（ - ）阴离子和纤维素链之间的H键的形成（ - ）阴离子进入纤维素纤维，特别是由于[OAC]（ - ）阴离子引起的纤维素链中夹紧H键的破裂在中间链H键之前进行。关于阳离子的作用，表明[C（2）MIM]（+）阳离子可以与纤维素相互作用，并且由于通过VAN DER WALS相互作用，特别是在第一溶剂中的堆叠效果而稳定分离的纤维素链纤维素链的壳在ILS中。我们的研究结果表明，由于阴离子由于阴离子的破损而引发的刚性纤维素链的灵活性引起的伴有阴离子的分解过程开始，由于阳离子的插入，协同，以及溶解和分解过程，伴随溶出过程同时执行。

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