深入了解摩尔比和加水对氯化胆碱和尿素基低共熔混合物的性质及其纤维素溶胀能力的影响,Physical Chemistry Chemical Physics

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深入了解摩尔比和加水对氯化胆碱和尿素基低共熔混合物的性质及其纤维素溶胀能力的影响
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2022-11-10 , DOI: 10.1039/d2cp04119g
Juho Antti Sirviö ₁ , Riikka Haataja ₁ , Anu M Kantola ₂ , Terhi Suopajärvi ₁ , Henrikki Liimatainen ₁

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低共熔混合物和低共熔溶剂 (DES) 是用于木质纤维素材料预处理的有前途的绿色介质。它们可用于纤维素的溶胀，并进一步促进纤维素水解、衍生化和纤维素基（纳米）材料的生产。一些研究表明水可以参与DES纳米结构的形成；然而，尚不清楚额外的水如何影响 DES 的许多重要特性和功能，尤其是当化合物的摩尔比与共晶点组成不同时。在这里，在存在和不存在添加水的情况下，研究了显示不同摩尔比的氯化胆碱和尿素混合物的粘度、pH 值、电导率、溶剂化变色和溶剂化磁性溶剂参数以及纤维溶胀能力。粘度、pH 值和电导率测量表明水参与了氯化胆碱和尿素分子簇的形成。含水混合物的氢键受体值随着含水量的增加而增加，使用这两种方法获得的结果是一致的，表明它们适用于测定氯化胆碱-尿素混合物的氢键酸度。然而，溶剂化显色法和磁法测定的氢键碱度表现出几乎相反的趋势。对溶剂化磁性探针化学位移的仔细研究表明，氯化胆碱-尿素 (1:2) 混合物的化学环境保持恒定，直到 30 wt% 的水含量与之前的分子模拟一致。当在混合条件下用混合物处理纤维素纤维时，发现氯化胆碱-尿素混合物的非理想性和不存在水是有利的；然而，水性混合物在没有混合的情况下有效地增加了纤维素纤维的直径，并且含水混合物似乎是用于纤维素预处理的有吸引力的系统。

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Insights into the role of molar ratio and added water in the properties of choline chloride and urea-based eutectic mixtures and their cellulose swelling capacity

Eutectic mixtures and deep eutectic solvents (DESs) are promising green media for the pre-treatment of lignocellulose materials. They can be harnessed for the swelling of cellulose and further facilitate cellulose hydrolysis, derivatization, and production of cellulose-based (nano) materials. Several studies indicated that water can take part in the formation of the nanostructure of DES; however, it is still unclear how additional water influences many important properties and functioning of DES, especially when the molar ratio of compounds differs from the eutectic point composition. Here, viscosity, pH, conductivity, solvatochromic and solvatomagnetic solvent parameters, and fiber swelling capacity of choline chloride and urea mixtures demonstrating different molar ratios were investigated in the presence and absence of added water. The participation of water in the formation of molecular clusters with choline chloride and urea was indicated by viscosity, pH, and conductivity measurements. Hydrogen bond acceptor values of aqueous mixtures increased as a function of water content, and the results obtained using both methods were in line, indicating their suitability for the determination of hydrogen bond acidity of aqueous choline chloride–urea mixtures. However, hydrogen bond basicity determined by solvatochromic and magnetic methods exhibited almost opposite trends. The close investigation of the chemical shift of solvatomagnetic probes indicated that the chemical environment of the choline chloride–urea (1 : 2) mixture remained constant until the water content of 30 wt% was in line with previous molecular simulations. When cellulose fibers were treated with mixtures under mixing, the non-ideality of the choline chloride–urea mixture and the absence of water were found to be advantageous; however, aqueous mixtures efficiently increased the diameters of cellulose fibers in the absence of mixing, and water-containing mixtures appeared to be appealing systems for cellulose pretreatments.

更新日期：2022-11-10

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