The ability to dissolve cellulose, by using mixtures of ionic liquids, has been studied and compared with results obtained for the corresponding single ionic liquids. The ionic liquid mixtures tested were a 3:7 mol/mol mixture of 1-ethyl-3-methylimidazolium chloride ([C₂mim]Cl) and 1-ethyl-3-methylimidazolium acetate ([C₂mim][OAc]), and the eutectic mixture (i.e., a 5.1:4.9 mol/mol ratio) of [C₂mim]Cl and 1-butyl-3-methylimidazolium chloride (C₄mim]Cl). The amount of dissolved cellulose was investigated at three different temperatures (323, 348, and 373 K) for each system. The greatest amount of dissolved cellulose was obtained for the [C₂mim]Cl + [C₂mim][OAc] mixture, at 373 K, and it was 40 g per 100 g of solvent. Moreover, attempts were made to lower the viscosity of the resulting systems and improve the dissolution capacity by addition of dimethylsulfoxide (DMSO) as co-solvent. Results showed that addition of DMSO at 50 mol% allows the dissolution of even greater amounts of cellulose (up to 43 g per 100 g of solvent). To the best of our knowledge, this is the largest ever reported amount of dissolved cellulose in ionic liquid media. Additionally, physical properties (density, surface tension, and viscosity) of the investigated ionic liquid mixtures were determined and compared with the values of the corresponding parent salts. The dissolved cellulose could be easily reconstituted from its solution in ionic liquid mixtures by addition of water. The regenerated cellulose was characterized by powder X-ray diffraction (pXRD), thermogravimetric analysis (TGA), and optical microscopy. The analyses confirmed the conversion of the crystal structure of cellulose from cellulose I to cellulose II during the dissolution and regeneration process.

中文翻译：

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离子液体混合物作为纤维素溶解的更有效介质

已经研究了通过使用离子液体混合物溶解纤维素的能力，并将其与相应的单个离子液体获得的结果进行了比较。所测试的离子液体混合物是1：3--3-甲基咪唑鎓氯化物（[C ₂ mim] Cl）和1-乙基-3-甲基咪唑鎓乙酸盐（[C ₂ mim] [OAc]）的3：7 mol / mol混合​​物，以及[C ₂ mim] Cl和1-丁基-3-甲基咪唑鎓氯化物（C ₄ mim] Cl的低共熔混合物（即5.1：4.9 mol / mol比）。对于每个系统，在三个不同的温度（323、348和373 K）下研究了溶解纤维素的量。对于[C ₂ mim] Cl + [C ₂mim] [OAc]混合物在373 K下加热，每100 g溶剂40 g。此外，已尝试通过添加二甲亚砜（DMSO）作为助溶剂来降低所得体系的粘度并提高溶解能力。结果表明，以50摩尔％的DMSO添加量可以溶解更多量的纤维素（每100克溶剂最多43克）。据我们所知，这是有史以来离子液体介质中溶解纤维素量最大的报道。另外，确定所研究的离子液体混合物的物理性质（密度，表面张力和粘度），并将其与相应母体盐的值进行比较。通过添加水，溶解的纤维素很容易从其在离子液体混合物中的溶液中复原。再生纤维素通过粉末X射线衍射（pXRD），热重分析（TGA）和光学显微镜表征。分析证实了在溶解和再生过程中纤维素的晶体结构从纤维素I转化为纤维素II。