共軛奈米分子之構型與自組裝形貌控制

Abstract

生物材料與人工合成材料領域中，分子於三圍空間的排列與其功能性有極大的關聯，許多文獻中提到，分子的構型會對於材料在空間中的自組裝產生極大的影響，有鑒於此現象的發現，許多人工設計的分子可藉由構型的調控改變其自組裝之固態形貌，加以達到多樣功能性的目的。 本研究採用MNP此一新興發展的超分子領域，試圖了解構型改變對其自組裝結構的影響，研究中使用的MNP是屬於對稱六加成C60體系，其中化合物結構包含：核心單元C60、外圍共軛芳香環硬鏈結構（T2A、C12T2A）以及連接架橋柔性鏈。透過分子模擬軟體的幫助，本研究發現此類共軛體系之MNP具有多樣的分子構型，其中包含具有高對稱性的Th星狀構型，以及多種不同的對稱性（C2、C3）的棒狀構型，雖然此分子系統中具有如此多樣的分子構型及對稱性，但其中構型與固態自組裝形貌的關聯仍未被研究的分常透徹。 本研究探討有關影響共軛MNP的自組裝的因素，依據一系列的實驗結果總結，MNP間的分子作用力（pi-pi interaction）以及其分子構型對於固態形貌的影響，有極高的關聯性。藉由改變MNP上的化學結構（有無碳鏈）可以有效得調整作用力的大小，而此會直接影響到分子的構型改變。當MNP系統中的作用力弱時，分子構型會呈現星狀結構，進一步使固態形貌產生具有高規則度的蜂巢狀陣列。而當MNP系統中的作用力強度提高，分子構型會轉變成具有C3對稱性的棒狀構型，並排列形成一規則狀態的二維結構，形成具有三方晶系的空間結構，且研究中同樣也發現，藉由溶劑的幫助，MNP系統中作用力較低的分子同樣能形成規則固態結構，故此棒狀MNP構型之固態規則結構，其具有最穩定的能量狀態。 因此透過本研究的實驗結論可得知，MNP的構型與改變構型的驅動力，對於此類超分子材料的固態形貌具有非常大的影響力。

The three dimensional (3D) arrangement of the constituent units of nano-sized molecules determines the functions of natural and artificial molecules. At different length scales, the molecular topology and supramolecular assembles of molecules determine the spatial arrangement of their constituent units. Constructed with a spherical core and multiple conjugated coronal units, 3D conjugated molecules have been developed as useful materials in optoelectronic and biomedical applications. Because of their nanometer molecular size, these molecules are also considered as molecular nanoparticles (MNPs), and used as important building block for giant molecules. However, because of their complex molecular structures, the self-assembly behavior and supramolecular structure of MNPs remain unclear. In this study, the key factors for the supramolecular behaviors of conjugated MNPs were studied. From the microscopic and diffraction results, we concluded that the intramolecular interaction among the peripheral conjugated arms and the molecular symmetry are determinative to the molecular topology and the supramolecular structures of MNPs. When the intramolecular interaction is weak, the MNP adopts a star-like topology with Th symmetry. These star MNPs interact isotropically to give a highly order honeycomb (HC) morphology. On the contrary, when the intramolecular interaction is strong, the MNP adopts a rod-like topology with C3 symmetry. These rod-MNPs prefer to interact intermolecularly in the horizontal direction, and pack into a trigonalcrystal lattice. Annealing the thin film of the MNP turns the HC morphology to the trigonallattice, suggesting that the rod conformation and the trigonal lattice are more energetic favorable. The molecular symmetry and how the MNPs interact intra- and intermolecularly are thus important in shaping the topology and supramolecular structures of conjugated MNPs.