水合金属盐低共熔溶剂室温溶解纤维素的分子动力学机制  

Molecular dynamics mechanism of metal salt hydrate-based deep eutectic solvent to dissolve cellulose at room temperature

作　　者：王雷 楼雨寒 童志函 孟娟 史晓超 曹凯玥 夏芹芹 于海鹏[1] WANG Lei;LOU Yuhan;TONG Zhihan;MENG Juan;SHI Xiaochao;CAO Kaiyue;XIA Qinqin;YU Haipeng(Key Laboratory of Bio-based Material Science and Technology(Ministry of Education),Material Science and Engineering College,Northeast Forestry University,Harbin 150040,China)

机构地区：[1]东北林业大学材料科学与工程学院,生物质材料科学与技术教育部重点实验室,哈尔滨150040

出　　处：《林业工程学报》2022年第4期64-71,共8页Journal of Forestry Engineering

基　　金：国家杰出青年科学基金(31925028)。

摘　　要：纤维素的溶解是提高其加工性和功能化的关键步骤,寻找能够实现纤维素室温有效溶解的低成本溶剂一直是业界期望和科研目标。笔者发现由氯化锌、甲酸和水组成的水合金属盐低共熔溶剂可在室温下有效溶解纤维素,借助分子动力学模拟,从氢键数目、径向分布函数及均方根偏差等方面探究了溶剂组分-结构关系对纤维素溶解的影响,在分子尺度解析了该溶剂对纤维素溶解的作用机制。模拟结果显示,纤维素间的氢键作用减弱,而溶剂与纤维素表面羟基形成较多的氢键。此外,相比于氯化锌和水,甲酸在纤维素表面羟基具有更强的作用,而水与氯化锌易形成金属盐水合壳层,与甲酸共同作用促进纤维素的高效溶解。纤维素溶解宏观图和偏光显微镜图显示了该溶剂在室温下可将纤维素溶解为透明溶液,通过理论计算与试验数据相结合确定了最优溶剂物质的量比(氯化锌∶甲酸∶水=1∶3∶2)。相比纤维素原料,再生纤维素的聚合度略有下降,晶型由Ⅰ型转变为Ⅱ型。通过傅里叶红外光谱和固体核磁波谱发现,再生纤维素保留了化学结构的完整性并发生了部分酯化反应。此外,再生纤维素具有较好的热力学性能(最大热降解温度约为332℃)。综上结果证明了水合金属盐低共熔溶剂对纤维素溶解的高效性,拓宽了溶剂选取的范围。As a new processing technology, cellulose dissolution is the key step to improve its compatibility with different matrixes and the value-added applications. Especially in recent years, the search of a low cost and green solvent for effectively dissolving cellulose at room temperature has become the industrial expectation and the goal of scientific research. We found that the acidic metal salt hydrate-based deep eutectic solvent composed of zinc chloride, formic acid and water could effectively dissolve cellulose at room temperature. However, the relationship of the acidic metal salt hydrate-based deep eutectic solvent and cellulose dissolution mechanism remains unclear. We investigated the relationship between structure activity of this solvent system and cellulose dissolution by the molecular dynamics simulation. In detail, we mainly explored the effect of composition-structure relationship of solvent on cellulose dissolution from the aspects of the hydrogen bond number, radial distribution function and root mean square displacement. The results of simulation experiments showed that the hydrogen bonds of cellulose became weak while hydrogen bonds between cellulose and solvent enhanced along with the increasing of simulation time. In addition, formic acid had stronger distribution on the hydroxyl surface of cellulose than that of other components. Especially, melt salt(ZnCl;) and water were more inclined to form metal salt hydrate that acted on cellulose together with formic acid. Benefits from above solvent effect, cellulose tended to disperse from an ordered structure to a disordered structure by the cleavage of cellulose hydrogen network. The digital images and polarizing microscope of cellulose dissolution showed that the acidic metal salt hydrate-based deep eutectic solvent system could effectively dissolve cellulose into transparent solution at room temperature. Through the combination of the molecular dynamic simulation and experimental verification, the optimal solvent for dissolving cellulose at room tem

关 键 词：纤维素 分子动力学模拟 金属盐 低共熔溶剂 室温溶解 

分 类 号：TQ352[化学工程]