水溶液中自组装螺旋聚电解质相行为的研究

发布时间：2018-05-05 04:21

本文选题：超分子自组装 + 螺旋结构　；参考：《中国科学技术大学》2017年博士论文

【摘要】：自组装聚电解质是由小分子组装单元通过弱相互作用力(非共价键作用力)形成的超分子聚合物,并且在溶液中可以电离为表面带电的聚离子和带相反电荷的反离子。自组装螺旋聚电解质,即具有螺旋结构的自组装聚电解质。它既保留了自组装体系的超分子特性又带来了表面电荷非均匀分布以及绕轴向旋转等螺旋结构的特点,提供了研究水溶液中聚电解质相互作用以及聚集行为的独特的模型体系。同时由于其与生物大分子比如普遍研究的DNA具有相类似的结构特性等因素受到科学工作者的广泛关注。众多关于螺旋聚电解质的研究工作仅仅关注小分子单元形成单个超分子结构的行为,即自组装的初级结构。然而如何让自组装初级螺旋聚电解质形成更高级的周期结构的机制以及影响因素等相关方面的研究仍处于起步阶段。基于以上背景,本论文工作以自主合成的C3对称三羧酰胺分子在水溶液中形成的自组装螺旋带电纳米管作为研究对象系统的研究了其在稀溶液中的介观相行为;更高级四方周期结构的形成机制以及结晶过程;同时研究了自组装带电螺旋纳米管形成的四方结构对反离子的种类、大小等性质的响应。主要研究内容及结果如下:1.研究了稀溶液中超分子自组装螺旋纳米管的介观相行为,以及相行为对陈化时间和外加离子的响应。超分子螺旋纳米管在水溶液中首先形成短程位置有序、角向无序的中间态六角液体相。通过增加陈化时间或者引入NaCl盐,中间态的六角结构会转化为稳定的位置高度位置有序的四方相。中间态对初态溶液的状态比如溶液的浓度、反离子的种类非常敏感。从六角结构到四方相的转变是由于角向关联以及带电螺旋纳米管沿着轴向的相对旋转造成的。角向关联来源于带电螺旋结构间静电相互作用的角向作用部分。稳定态的四方结构并不会随着离子浓度,反离子的种类等发生显著变化。与生物大分子以及胶体结晶相比,在我们体系中观察到的缓慢的结晶过程以及稳定的终态为溶液中制备结晶材料提供了新的思路。不仅有助于深入理解聚电解的相行为而且对溶液中软物质的组装过程有广泛的指导意义。2.系统地研究螺旋带电超分子纳米管形成长程有序结构的机制以及结晶过程。棒状的超分子带电纳米管如何由均匀的纳米管溶液组装形成稳定的四方聚集体。研究了溶液的浓度对超分子带电螺旋纳米管的结晶过程的影响。反离子在带电螺旋纳米管结晶过程中所发挥的作用,以及超分子带电螺旋纳米管如何通过调控角向的旋转来实现调控角向关联。溶液中的超分子纳米管经历短程位置有序、二维长程位置有序及角向有序调整的结晶过程最终获得三维长程位置有序多级结构,在溶液中形成独特稳定的四方相。结果对理解溶液中的结晶过程以及液晶相行为的调控具有重要的借鉴意义。3.对比研究两种不同的反离子对稳定的四方晶格的影响。出乎意料的,在共离子相同的条件下体积较小的、亲水的、与带电螺旋纳米管表面的羧酸基团有较强亲和力的碱金属阳离子会导致带电螺旋纳米管形成的四方晶格发生各向异性的膨胀,并且膨胀的程度与反离子与羧酸基团的亲和程度呈正相关。在此情形下,共离子会不同程度的影响四方晶格内部的有序程度。然而当用体积较大的、疏水的、与带电螺旋纳米管表面的羧酸基团亲和力较差的季铵阳离子替换单价的碱金属阳离子时四方晶格发生各向同性的收缩并且无共离子效应。以上结果说明在高度带电的,紧密排列的聚电解质体系中存在非常明显的离子关联,独特的离子效应不仅对于强静电作用下的离子特异性有借鉴意义而且可以用来指导通过离子调控聚电解结构的相关生命科学过程。
[Abstract]:Self assembled polyelectrolyte is a supramolecular polymer formed by a small molecule assembly unit through a weak interaction force (non covalent bond force) and can be ionized into a surface charged polyion and reverse charge in the solution. Self assembled spiral polyelectrolytes, that is, a self assembled polyelectrolyte with a spiral structure, are retained. The supramolecular characteristics of the self-assembly system also bring about the characteristics of the nonuniform distribution of surface charge and the spiral structure around the axis, which provide a unique model system to study the interaction and aggregation of polyelectrolyte in aqueous solution. At the same time, it has a similar structure to the biological macromolecule, which is similar to the commonly studied DNA. A large number of research work on helix polyelectrolytes is concerned only with the behavior of small molecular units to form a single supramolecular structure, that is, the primary structure of self-assembly. However, how to make self assembled primary helix polyelectrolytes form a more advanced periodic structure and influence factors, etc. The research is still in the initial stage. Based on the above background, the self assembled spiral charged nanotube formed by the self synthesized C3 symmetric three carboxamide molecule in the aqueous solution is used as the research object to study the mesoscopic phase behavior in the dilute solution, the formation mechanism of the higher tetragonal periodic structure and the crystallization. The main research contents and results are as follows: 1. the mesoscopic phase behavior of supermolecule self assembled spiral nanotube in dilute solution, and the response of phase behavior to the aging time and the added ion are investigated. The nanotube is first formed in a water solution with a short range position and a disordered six angle liquid phase in the middle state. By increasing the aging time or introducing NaCl salt, the six angle structure of the intermediate state will be transformed into a stable and highly ordered Quartet phase. The state of the intermediate state to the state of the initial state solution, such as the concentration of the solution, is not the type of the counter ion. The change from the six angle structure to the Quartet phase is caused by the angular correlation and the relative rotation of the charged spiral nanotube along the axial direction. The angular correlation comes from the angular action part of the electrostatic interaction between the charged helical structures. The Quartet structure of the stable state does not occur with the concentration of the separated ions and the types of the reverse ions. Compared with the biological macromolecules and colloidal crystals, the slow crystallization process observed in our system and the stable end state provide a new idea for the preparation of crystalline materials in the solution. It not only helps to understand the phase behavior of the electrolysis but also has a broad guiding significance for the.2. system in the process of the assembly of soft substances in the solution. The mechanism of the long-range ordered structure of the spiral charged supermolecular nanotube and the crystallization process are studied. How can the rod like supermolecule nanotube be assembled by the uniform nanotube solution to form a stable Quartet aggregate. The effect of the concentration of the solution on the crystallization of the supermolecule charged spiral nanotubes is studied. The role of the spiral nanotube in the crystallization process and how the supermolecule charged spiral nanotube can regulate angular correlation by regulating the rotation of the angular direction. The supermolecular nanotube in the solution has a short range position order, the two-dimensional long range position order and the angular ordering process finally obtain the three-dimensional long range position order. The formation of a unique stable tetragonal phase in the solution is an important reference for understanding the crystallization process in the solution and the regulation of the behavior of liquid crystal phase..3. contrasts and studies the effects of two different anti ions on the stable tetragonal lattice. The alkali metal cation with strong affinity on the surface of the charged spiral nanotube leads to anisotropic expansion of the tetragonal lattice formed by the charged spiral nanotube, and the degree of expansion is positively correlated with the affinity between the anti ion and the carboxylic acid group. In this case, the Co ions will affect the tetragonal lattice in varying degrees. An isotropic contraction and no Co ion effect occurs when a larger, hydrophobic, quaternary ammonium cation is replaced by a quaternary ammonium cation with poor affinity to the carboxylic acid group on the surface of a charged spiral nanotube. The above results show that the highly charged, closely arranged polyelectrolysis is shown. There is a very obvious ion correlation in the mass system. The unique ion effect is not only useful for the ion specificity under the strong electrostatic action, but also can be used to guide the related life science process of the electrolysis structure through ion regulation.

【学位授予单位】：中国科学技术大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O631

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