Supramolecular Structures Of Self-Assembled Dendron-Containing Hybrids

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.