结构可控区域选择性取代纤维素衍生物的分子设计、构效关系及应用研究

Preparation of uniform and controllable cellulose dirivatives is extremely complex, for the substituent randomly distributes in the glucosyl units and along the polymer chain. Therefore, the structure and structure-property relationship is very difficult to estimate and those would constrain the development of cellulose chemistry and materials. Regioselectively subtituted cellulose derivatives are sysnthesized to investigate the structure and structure-property relationship with protecting methods. As a sructure model, the regioselectively subtituted cellulose derivatives are used to explore simple, effcient testing technology. On the other hand, those derivatives could be used to study the properties of specific substituted cellulose derivatives as well. Meanwhile, the cellulose derivatives prepared under different conditions are compared and analysised,for studing the influence of substituent distribution on the structure and properties. Then the struture-property relationships of cellulose derivatives could be established. Novel materials with fascinating properties,such as optical, electronical, magnetical and biological activities, are synthesized with regioselectively subtituted cellulose derivatives as precursors. Those cellulsoe derivatives could be composited with functional materials. This project has important basic theoretical significance and practical value for cellulose dirivatives chemistry and molecular design, and furthur would conduct the chemical modification and application of other polysaccharide.

制备结构均一、精确可控的纤维素衍生物极其困难，成为制约纤维素化学及新材料发展的瓶颈。快速高效地确定纤维素衍生物微观结构和建立系统的构效关系是纤维素化学亟待解决的两大难题。本课题通过保护基团进行分子设计，控制取代基团在葡萄糖单元特定位置上取代，制备结构可控的区域选择性取代纤维素衍生物。以此为结构模型，根据纤维素衍生物葡萄糖单元羟基与高分子间氢键作用机理，探索简单、快速的检测方法，确定纤维素各取代位置平均取代度；并对比不同结构的纤维素衍生物，研究特定位置基团及其分布对性能的影响规律，建立系统的构效关系。以结构可控的区域选择性取代纤维素衍生物为前驱体，与具有电活性、生物活性物质复合制备功能材料，研究纤维素衍生物微观结构对功能材料的电性能、生物性能的影响。项目对纤维素化学及新材料设计具有重要的基础理论意义和实用价值，同时对其他多糖化学改性和应用具有理论指导意义。

制备结构均一、精确可控的纤维素衍生物一直是纤维素化学及新材料发展的一大难题，这极大限制了纤维素衍生物结构与性能之间构效关系的建立。本课题研究了最常用的几种纤维素酯、纤维素醚，如纤维素乙酸酯（CA）、羧甲基纤维素（CMC）和羟丙甲基纤维素（HPMC）的制备、结构与性能。研究表明取代度（DS）为2.5的均相离子液体制备CA与商业购买非均相CA的化学结构不同，但两组CA表现出的物理性质相似；通过保护基团进行分子设计，制备了DS在0.2-2.0之间、乙酰基分别取代在C-2,3位置和主要取代在C-6位置的系列CA.虽然两组CA随DS的变化规律相似，但具有相同DS的CA物理性质差别很大，如相同DS的2,3-O-CA的玻璃化转变温度提高35 oC、最大分解温度提高28 oC，并建立了CA结构与性能之间的构效关系；应用研究表明2,3-O-CA明显增加聚合物的热稳定性，且改变CA超滤膜的微观结构。制备不同结构的CMC，发现C-6位取代为主的CMC比C-2,3位取代为主的样品更适合作为乳液的稳定剂，而双取代的HPMC适用在固固相变材料中。