The weight-average molecular weights of six native cellulose samples in ionic liquids were determined through steady shear viscosity measurements in the ionic liquid butyl methyl imidazolium chloride. The intrinsic viscosity [ η ] in ethyl methyl imidazolium acetate (EMImAc) is measured using a gravity-driven glass capillary viscometer and found to be independent of temperature in the range of 30–80 °C, disproving a literature report of [ η ] in EMImAc, exhibiting a strong temperature dependence. Findings are contrasted with values of intrinsic viscosity in cupriethylenediamine hydroxide, the most widely used solvent to dissolve and analyze the molecular weight of cellulose pulps in industry. Differences are tentatively attributed to the different temporary association properties of cellulose chains in the two solvents. Finally, it is demonstrated that cellulose adsorbs at the air/solution interface in three different ionic liquids to create a viscoelastic liquid interfacial layer of higher concentration. Adsorption at the air/solution interface gives an extra contribution to the measured torque in various rotational rheometer geometries, which apparently simply adds to the torque from the pure bulk solution.

中文翻译：

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离子液体中天然纤维素溶液特性粘度的测定

六种天然纤维素样品在离子液体中的重均分子量是通过在离子液体丁基甲基咪唑氯化物中的稳定剪切粘度测量来确定的。使用重力驱动的玻璃毛细管粘度计测量乙基甲基咪唑醋酸盐 (EMImAc) 中的特性粘度 [ η ]，发现其在 30–80 °C 范围内与温度无关，反驳了文献 [ η ] 在EMImAc，表现出强烈的温度依赖性。结果与氢氧化铜二胺的特性粘度值形成对比，氢氧化铜是工业中用于溶解和分析纤维素纸浆分子量的最广泛使用的溶剂。差异暂时归因于纤维素链在两种溶剂中不同的临时缔合特性。最后，结果表明，纤维素在三种不同的离子液体中吸附在空气/溶液界面上，以产生更高浓度的粘弹性液体界面层。空气/溶液界面处的吸附对各种旋转流变仪几何形状的测量扭矩有额外贡献，这显然只是增加了纯本体溶液的扭矩。