基于氢键竞争的秸秆纤维素可控溶解与多层次结构调控

Development of environmental friendly solvent for cellulose and manifestation of the dissolving mechanism constitute the main interesting research points in the domain of cellulose processing and utilizing, and the key problem lies in regulation of the hydrogen bond in its multistructure. In this project, new solvent is going to be developed for controllable dissolving straw cellulose and regulating its mutistructure by introducing hydrogen bond competition. Firstly, the function of hydrogen bond on multistructure formation of cellulose will be manifested by study the intra- and inter-molecular hydrogen bonds in presentative straw cellulose, such as rice straw cellulose in simulation together with systematic experiments. Secondly, we are going to find out how the added hydrogen acceptor participates in competition, dissociation and shielding different kinds of the hydrogen bonds by investigating the effluence of physical and chemical circumstances on the hydrogen bonds and the multistructure. Then, small size ion with strong negative, e.g. F- ion will be introduced into environmental friendly aqueous solution to discuss the characteristics of intra- and inter-molecular hydrogen bonds in cellulose as well as the physical and chemical process during the competing process of the hydrogen bonds in the complex formed in the aqueous solution. The proper aqueous solvent can then be designed toward certain cellulose. Finally, on account of mastering thermodynamics, rheologic behavior and process ability of the cellulose solution, the systematic methods will be established for controllable dissolving cellulose and regulating the micro- or nano structure of straw cellulose based on hydrogen bond competing and shielding process.

环保化的纤维素新溶剂及其溶解机理一直是纤维素加工和应用领域的研究热点，对纤维素多层次结构中的氢键调控则是实现其可控溶解和成型加工的关键。本项目以农作物秸秆纤维素为研究对象，希望通过引入氢键竞争体系实现其可控溶解和多层次结构调控。首先，通过模拟计算和实验研究，对典型秸秆纤维素的分子内和分子间氢键进行系统研究，揭示氢键在秸秆纤维素多层次结构构筑中的作用机理。其次，通过研究环境条件等物理化学作用对秸秆纤维素中氢键和多层次结构的影响规律，阐明外加氢键基元参与纤维素分子中氢键竞争、解离和屏蔽机制。在水等环保型溶剂体系中，引入F-离子等小体积、强电负性基团，研究其对纤维素分子间/分子内氢键、以及水分子缔合体中氢键竞争的物理化学过程，优化出合理的水基纤维素溶剂体系及其适用的纤维素结构。对秸秆纤维素溶液的热力学、流变学、加工等性能进行研究，建立基于氢键竞争和屏蔽作用的秸秆纤维素可控溶解和微纳结构调控方法。

天然纤维素新溶剂及其溶解机理是天然高分子材料和基于可再生资源高分子领域的研究热点。基于对科学问题突破，研制环保，高效新溶剂预期对纤维素纤维纺丝，成膜等材料领域带来重大革新。本项目针对纤维素溶解过程中氢键的竞争与有效屏蔽这一科学问题，通过系统的实验研究和模拟计算相结合开展研究，在氢键在秸秆纤维素多层次结构构筑中的作用机理及氢键竞争和屏蔽的纤维素溶解机理与调控机制取得学术突破，取得的研究结果主要包括：（1）将尿素引入四丁基氢氧化铵水溶液体系的研究发现尿素可作为亲疏水的调控剂。通过调控尿素的添加量，复合溶剂体系的双亲性可以被调控，从而可以控制其对纤维素的溶解性，并获得纤维素纳米晶。（2）通过分子动力学模拟，将纤维素溶剂化过程实现可视化评价，通过溶剂层厚度的分析对温度，季胺碱中烷基碳数目等影响因素做出的分析预测与实验结果高度吻合。（3）根据分子动力学模拟研究的指导，找到一种助剂，将其引入四丁基氢氧化铵水溶液实现天然纤维素室温条件下快速溶解。.通过项目资助，课题组发表SCI论文15篇（IF≥3的8篇），申报国家发明专利6项，其中1项已获授权；参加国际学术会议4人次；参加学术交流4次，培养博士研究生1名，硕士生6名。