具有外界刺激响应的核酸热致液晶材料的合成和性能研究

Over the last decades, water-based lyotropic liquid crystals (LLCs) of nucleic acids have been extensively investigated because of their important role in biology. Alongside, solvent-free thermotropic liquid crystals (TLCs) from DNA are gaining great interest, owing to their relevance to DNA-inspired optoelectronic applications. Up to now, however, only the smectic phase of DNA TLCs has been reported. The development of new mesophases including nematic, hexagonal, and cubic structures and investigation of stimuli responsive behaviors for DNA TLCs remains a significant challenge, which thus limits their technological applications considerably. In this project, we aim to fabricate a new type of DNA TLCs that are formed by electrostatic complexation of anionic oligonucleotides and cationic surfactants. A series of DNA and surfactants with different structures will be used to induce specific packing styles and turn intermolecular interactions for controlling TLC mesophase behaviors. Photomechanics of the DNA TLCs will be investigated based on the photoisomerization of the surfactant azobenzene moieties. Additionally, we plan to fabricate fluorescent DNA TLCs, which is useful for study of electrofluorochromic behaviors. Thus, the investigation of stimuli-responsive DNA TLCs holds great potentials for the construction of smart biomaterials.

基于核酸分子的溶致液晶在生物及生物医学领域具有重要的应用价值。最近几年研究发现在无水环境中核酸可以形成热致液晶材料，并且在电场作用下具有电致变色效应，因而新型核酸热致液晶激起了科学家们的研究兴趣。但是目前只有关于近晶型核酸液晶的报道，如何丰富核酸热致液晶的晶相以及研究它们在外界（光电磁力学）刺激下的响应行为并探索它们在生物智能材料领域的应用具有重要的意义。本课题计划通过对核酸进行化学修饰引入柔性的脂肪链分子制备核酸热致液晶材料，并且试图通过控制核酸分子和柔性脂肪链的结构，进而改变核酸分子的不同取向以实现对核酸热致液晶相的调控。本课题将通过在柔性脂肪链部分引入偶氮苯基团试图研究核酸热致的液晶的光致力学行为。另外通过改变核酸的碱基序列，实现它们的荧光特性以达到对核酸热致液晶的电致荧光变色行为的调控。从而为构建基于核酸热致液晶的智能材料奠定坚实的基础。

项目通过发展不同主体材料，利用静电作用结合具有柔性链段表面活性剂，成功制备刚性与柔性区域交替的热致液晶复合物。研究实现了基于柔性链段引入的偶氮苯表面活性剂制备热致液晶，表现出基于外界力响应改变液晶结构，并且这种改变可以长久的保持，实现对外加剪切力的响应及存储。此外，改变核酸序列，引入人工柔性疏水链修饰碱基，外加含脂肪链表面活性剂制备液晶复合物，表现出电致荧光变化行为，通过循环施加关闭电场，表现出液晶稳定性。此外实现对稀土纳米晶表面进行共价修饰柔性链段，实现了在无溶剂条件下的流体行为，该系列稀土纳米晶介晶相表现出偏振激发的上转换及下转换发光特性。同时发展了多种基于长链DNA的可塑性液晶凝胶制备，应用于复杂形状环形中实体瘤的治疗，还可实现生物体内响应性分解、复杂形状可塑性及优异力学性能。基于以上结果对新一代微型智能光电器件及智能响应性、形状记忆可塑材料的开发具有借鉴价值。