| Popis: |
In biological systems, it is well-known that the activity and function of biomacromolecules are dictated not only by their primary chemical structures, but also by their secondary, tertiary and quaternary hierarchical structures. Achieving similar levels of control in synthetic macromolecules has yet to be demonstrated. In 1960, Feynman raised a fundamental question: “What would the properties of materials be if we could really arrange the atoms the way we want them?” It is difficult to answer this question at truly atomic level. However, by taking the advantage of the unique giant molecular system recently developed by our group, we are trying to answer it at the “nanoatom” length scale in this dissertation. We started with design, syntheses and crystal structure analyses of three series dyads of sphere-plate giant shape amphiphiles with distinct shapes and precise chemical linkages based on C60-triphenylene (sphere-triangle), C60-perylene diimide (sphere-rectangle) and C60-Porphyrin (sphere-square). We then developed a novel synthetic methodology using orthogonal “click” chemistries, strain-promoted azide-alkyne cycloaddition (SPAAC), oxime ligation and thiol-ene click coupling (TECC), for preparing a library of polystyrene (PS)-polyhedral oligomeric silsesquioxane (POSS) giant surfactants with precisely arranged nano-building blocks. The heterogeneity of primary chemical structure can be precisely controlled and is reflected in the self-assembled supramolecular structures in bulk or in solution. The composition (the volume fraction of hydrophilic “nanoatoms”) and functionality are the crucial to determine the assembled structures, illustrated by a series of linear configured PSm-(XPOSS)n. The functionality and topology are also found to affect the assembled structures when the volume fractions are identical, demonstrated by several linear and branched PSm-(XPOSS)n giant surfactants. Furthermore, the sequence effect is explored by comparing the self-assembly behaviors of a pair of sequence isomers. In order to step further answering Feynman’s inquire, we extend the synthetic method to prepare truly precise “nanoatom” chains or dendrimers with polydispersity Ð equal to 1, which also form varies order supramolecular structures as we tune their primary chemical structures. Our work offers a promising opportunities to manipulate the hierarchical heterogeneities of giant molecules via precise and modular assemblies of various nano-building blocks, and provides a platform for making precise nanostructures that are not only scientific intriguing but also technologically relevant. |
