School of Chemistry and Environmental Science, Key Laboratory of Green Chemical Media and Reactions, Ministry of Education Henan Normal University, Xinxiang, Henan 453007, China.
Chemphyschem. 2012 Sep 17;13(13):3126-33. doi: 10.1002/cphc.201200286. Epub 2012 Jun 21.
In recent years, great progress has been made in the dissolution of cellulose with ionic liquids (ILs). However, the mechanism of cellulose dissolution, especially the role the IL cation played in the dissolution process, has not been clearly understood. Herein, the mixtures of cellulose with a series of imidazolium-based chloride ionic liquids and 1-butyl-3-methyl pyridinium chloride ([C(4)mpy]Cl) were simulated to study the effect that varying the heterocyclic structure and alkyl chain length of the IL cation has on the dissolution of cellulose. It was shown that the dissolution of cellulose in [C(4)mpy]Cl is better than that in [C(4)mim]Cl. For imidazolium-based ILs, the shorter the alkyl chain is, the higher the solubility will be. In addition, an all-atom force field for 1-allyl-3-methyl imidazolium cation (Amim) was developed, for the first time, to investigate the effect the electron-withdrawing group within the alkyl chain of the IL cation has on the dissolution of cellulose. It was found that the interaction energy between Amim and cellulose was greater than that between C(3)mim and cellulose, indicating that the presence of electron-withdrawing group in alkyl chain of the cation enhanced the interaction between the cation and cellulose due to the increase of electronegativity of the cations. These findings are used to assess the cationic effect on the dissolution of cellulose in ILs. They are also expected to be important for rational design of novel ILs for efficient dissolution of cellulose.
近年来，离子液体（ILs）溶解纤维素取得了巨大进展。然而，纤维素溶解的机制，特别是 IL 阳离子在溶解过程中的作用，尚未得到明确的理解。在此，模拟了纤维素与一系列基于咪唑的氯化 IL 和 1-丁基-3-甲基氯化吡啶([C(4)mpy]Cl)的混合物，以研究改变 IL 阳离子的杂环结构和烷基链长度对纤维素溶解的影响。结果表明，纤维素在[C(4)mpy]Cl 中的溶解优于在[C(4)mim]Cl 中的溶解。对于基于咪唑的 IL，烷基链越短，溶解度越高。此外，首次开发了用于 1-烯丙基-3-甲基咪唑阳离子(Amim)的全原子力场，以研究 IL 阳离子烷基链上吸电子基团对纤维素溶解的影响。结果发现，Amim与纤维素之间的相互作用能大于C(3)mim与纤维素之间的相互作用能，表明阳离子烷基链上吸电子基团的存在由于阳离子的电负性增加，增强了阳离子与纤维素之间的相互作用。这些发现用于评估阳离子对 IL 中纤维素溶解的影响。它们也有望为合理设计新型 IL 以有效溶解纤维素提供重要依据。
