【作者】 刘波；

【导师】 王维；

【作者基本信息】 南开大学 ， 高分子化学与物理， 2013， 博士

【摘要】 自组装作为生命体中各种复杂生物结构形成的基础,在过去的数十年中,已经得到了材料科学、生命科学、信息科学、纳米科学等领域科学家的广泛关注。调控自组装材料的结构和功能随之成为一个重要的课题。杂化材料由两种纳米或分子级别成分组成,强调不同组分性能上的互补以及协同效应,从而展现出新的特性和功能。杂化物的自组装材料由此成为我们关注的焦点。在众多的构筑基元中,树枝状分子由于其独特而确定的分子形状以及多重功能性,在多样的环境中展现出新颖有趣的化学和物理性质以及自组装行为。我们通过借鉴生命体系中的分子识别和自组装思想,设计合成具有不同形状和性质的树枝状分子和无机簇等构筑单元结合的杂化分子,进而利用弱相互作用及其协同效应构筑具有特定空间结构和特殊功能的多层次超分子体系。本研究中,我们采用了树枝片分子(Dendron)、富勒烯(C60)、多金属氧酸盐(POMs)等构筑单元来构筑结构新颖、性质独特的杂化分子。结构上的创新在于沙漏形、蝴蝶形、羽毛球形分子的设计。第一类杂化分子是由两个不同的Dendron连接而成的嵌段树枝状大分子。通过控制两个Dendron的尺寸和功能基团的数目,调控其所构筑的本体超分子结构。从功能性质方面考虑,POMs和C60是很好的结构单元同时具有丰富的光、电和磁的功能特性,在催化、生物医药及纳米科技领域有着广阔的应用前景。它们的有机改性是重中之重,增强性能的同时扩展了体系的自组装结构及应用范围。我们在Dendron中嵌入POM或者与一个C60连接,制备了第二和第三类杂化分子。这些分子通过自组装形成有序的超分子结构,促使POM和C60也能够有序地排列。获得的结果不仅可以加深对树枝状大分子的分子结构和自组装性质关系的理解,同时也可通过自组装性质获得功能基团有序排列的、具有协同效果的、拓展了应用范围的功能材料。本文着重研究三类杂化分子的几何形状与组装形成超分子结构和性质间的关系,为发展新型的功能材料奠定了基础。首先,我们采用收敛法精确合成了含长烷基链的三代聚氨酯酰胺Dendron (g3-PUA)和三代聚脂肪醚Dendron(g3-PMDC),并将PUA与PMDC共价键相连接得到的形状可调控的杂化Dendron(g3-PUA-b-g3-PMDC),以及脱去PMDC上的保护基团得到两亲化的(g3-PUA-b-g3-PMDC(OH)8),实现调控分子的形状和两亲性的目标。这些操控实际上导致了样品在烷基链从结晶到熔融的过程中,超分子结构从柱状到层状最后到有趣而奇妙的Gyroid结构的演变。我们仔细地讨论了分子形状、极性强弱和烷基链结晶在超分子结构形成过程中起到的重要作用。具体的研究结果为：(1)端基为羧基g3-PUA呈现扇片形状,在PUA树枝片分子间多重氢键和端羧基氢键的主导作用下,在烷基链的结晶和熔融态下都聚集形成稳定的柱状结构；(2)g3-PUA-b-g3-PMDC呈现楔形扇片形状,由于烷基链结晶,形成了稳定的层状结构；(3)两亲化g3-PUA-b-g3-PMDC(OH)8为楔形扇片,八个端羟基的相互作用下,在烷基链结晶时形成层状结构,而在熔融时形成稳定的Gyroid结构。这些研究结果让我们对超分子纳米结构的形成机理有了更深的理解,即可以通过精确调控分子的形状、极性和官能团来构筑具体而精确的超分子结构,尤其是Gyroid结构。其次,我们研究了Anderson型POM与g2-PUA杂化大分子在溶液中形成有机凝胶的超分子结构和机理。我们将两个g2-PUA通过共价键接枝到有机改性的Anderson型POM的两端上,获得一种含POM的蝴蝶形杂化凝胶因子。由于g2-PUA与POM在尺寸上匹配,以及g2-PUA的多重氢键和质子化POM结晶能力的协同作用,驱动凝胶因子在有机溶剂中自组装成高度有序的单分子层杂化带状聚集体,相互交叉重叠构筑三维网络束缚溶剂分子,从而形成稳定的杂化有机凝胶。在带状聚集体中POM夹在g2-PUA层间,空间受限不能三维结晶,而是堆积成有序的单簇层,使得带状聚集体呈现很强的刚性。我们的研究证明了利用杂化分子中有机无机组分的协同效应可以软化POM簇。考虑到它们本身具有的功能,本研究利用超分子自组装精确调控POM簇的排列,有利于其性能的优化。最后,我们将g3-PUA与C60通过共价键构筑了羽毛球形杂化大分子,利用g3-PUA规整的形状和分子骨架上的多重作用力来指导杂化大分子的自组装行为,实现了富勒烯的一维有序排列。在研究它的溶液自组装时,发现调节溶剂种类、比例、以及浓度均会对超分子聚集体的形貌产生很大影响。在不同比例的四氢呋喃和水混合溶剂体系中获得了含C60杂化大分子的纳米带和纳米管。在异丙醇中形成空心多层花状聚集体。在甲苯中形成球形胶束,并且随着浓度增加胶束尺寸增大。在N,N-二甲基甲胺中形成超分子凝胶,含有均匀刚性的纤维结构。我们详细研究了带状超分子结构。由于树枝片与溶剂分子的相互作用,导致C60聚集在带状体的中间形成树枝片层夹心C60层的结构。树枝片中酰胺键和氨酯键间的多重氢键作用对于带状聚集体的形成起到了指导性的作用。通过分子模拟得出聚集单元的最小尺寸,并据此提出多级自组装过程的基本模型。我们的工作将功能性基团C60有序地排列在树枝状分子所提供的氢键等多重作用力的指导下形成的有序超分子聚集体中,制备了含有C60的微相有序材料,为实现光伏器件等复杂功能材料的设计提供了一个有效途径。更多还原

【Abstract】 Self-assembly as a basis for constructing a variety of complex biological structures in life, has gained extensive attention of many scientists in the field of material science, life science, information science, and nano science in the past decades. Manipulation on the structure and function of self-assembly materials since becomes an important topic. The hybrid materials are composed of two kinds of nano or molecular level components, emphasizing the complementary on the performance and synergistic effect of different components, thereby showing the new features and functionalities. The self-assembled hybrid materials thus have become the focus of our attention.In many units, due to its unique, defined molecular shape and multiple functionalities, dendrimers show novel and interesting chemical and physical properties and self-assembly behaviors in diverse environments. On the thought of the molecular recognition and self-assembly in the life system, we designed and synthesized hybrid molecules containing building unit of inorganic clusters and dendrons with different shapes and features by chemical synthesis method, then built hierarchical supramolecular systems with specific structure and special features using weak interactions and their synergistic effect.In this study, we used the dendrons, C60, polyoxometalates (POMs) to construct hybrid molecules with novel structures and unique properties. The structural innovation is to design the hybrid molecules with hourglass-, butterfly-, or badminton-shaped molecular architechtures. The first hybrid is composed of two dendrons different in chemical structure. Through the manipulation of the shape and amphiphilicity of the dendrons, we can obtain corresponding supramolecular structures. Considering the functional properties, POM and C60as well structural units with a diverse range of optic, electric and magnetic properties, have shown potential applications in catalysis, biotechnology and nanotechnology. The organic modification of POMs is the priority among related works, enhancing the performances as well as expanding the self-assembled structures and application. We introduced certain functional units such as POM and C60into dendrons, and then the second and third hybrids were prepared. These hybrids self-assembled into ordered supramolecular structrues, promopting POM and C60to be orderly arranged. The results obtained can not only enhance the understanding of the relationship of molecular structure of the dendrimers and self-assembly properties, but also help to develop new functional materials to extend application field with ordered structures and synergetic effects via self-assmbly process. This work focuses on the relationship of topological shape of three hybrids, supramolecular structures and properties, laying the foundation for developing new functional materials.First, we have accurately synthesized third generation dendritic poly(urethane amide)(g3-PUA) with long alkyl chains and benzyl end-capped third generation poly(methallyl dichloride)(g3-PMDC) with convergence method, and further covalently coupled them to obtain hybrid dendron g3-PUA-b-g3-PMDC, whose protective groups could be easily removed to obtain amphiphilic g3-PUA-b-g3-PMDC(OH)8, achieving the target of manipulating the molecular shape and polarity. This manipulation is actually resulted in the supramolecular structures from columnar to layered finally to the evolution of interesting and mysterious Gyroid structure in the alkyl chain melt and crystallized samples. We carefully discussed the important role of molecular shape, polarity, and alkyl chain crystallization played in the formation of the supramolecular structure. Specific results are as follows:(1) g3-PUA showing a fan shape, under the leading role of intermolecular multiple hydrogen bonds and carboxyl, formed a stable columnar structure in the samples with crystallized and melting alkyl chains;(2) g3-PUA-b-g3-PMDC presents the wedge shape, in which the alkyl chain crystallization lead to the formation of stable lamellar structure;(3) amphiphilic g3-PUA-b-g3-PMDC (OH)8with wedge shape, under the interaction of eight terminal hydroxyl group, form a lamellar structure in the alkyl chain crystallized sample, and stable Gyroid structure in the melt. The results of our study make a deeper understanding of the mechanism of the formation of supramolecular nanostructures, which can construct specific and accurate supramolecular structures, especially the Gyroid structure, through the precisely control of molecular shape, polarity and functional groups.Next, we studied the supramolecular structure and mechanism of organic gel formed by the hybrid molecules of Anderson type POM and g2-PUA Dendron. We put the PUA dendron covalently onto organically modified Anderson POM cluster, obtaining a POM-containing hybrid gelator. Driven by the size matching of two components, synergist of multiple intermolecular interactions and the crystallization of protonated POM, the protonated hybrid gelator self-assembled into high ordered monolayer hybrid ribbons in organic solvent.Then,supramolecular ribbon through-mutual overlapping into three-dimensional network bounding solvent molecules, formed stable hybrid organic supramolecular gel. Because of confined space, the polyoxometalate layer can not be crystallized in three-dimensional space, therefore, accumulated in two PUA interlayers, while the nanoribbons showed strong rigidity. Our results demonstrate that using the synergistic effect of inorganic and organic components of hybrid molecules can soften the POM clusters. Considering their funtionalilies, our study precisely controlled the arrangement of POM via self-assembly, propitiously to optimize its performance.Finally, the badminton-like molecule was synthesized via g3-PUA dendron incorporating with an organically modified C60moiety. Directed self-assembly of the hybrid has been successfully utilized to tune the spatial ordering of C6o through the shape and multiple interactions provided by molecular skeleton. The manipulation of different solvent, proportion, and concentration will have a. great influence on the morphology of supramolecular aggregates by solution self-assembly. We obtained one-dimensional fullerene nanoribbons and nanotubes in tetrahydrofuran and water mixed solvent. We found the formation of multi-layer hollow flower-like aggregates in2-propanol, and spherical micelles in toluene, with the increasing concentration of which micellar size increased. Supramolecular gel formed in DMF with uniformly rigid ribbon structure. We carefully studied the nanoribbons. Due to the interaction of the dendrons and solvent molecules, fullerene molecules can form sandwich layer in the middle of ribbons. The multiple hydrogen bonds between the amide and urethane bonds of dendrons play a directional role for anisotropic grown ribbons. We estimated the minimum size by molecular simulation and calculation, and accordingly put forward the basic model of hierarchical self-assembly process. Our work put functional fullerene orderly into the ordered aggregates formed under the guidance of multiple interactions provided by dendrons, and prepared C60-containing ordered supramolecular materials, which have provided an effective route to design functional materials for potential applications of photovoltaic devices etc.更多还原