Macroscopic Self Assembly Through Interactive-surface-area And Coordinate Covalent Interactions

Macroscopic supramolecular assembly has attracted growing attention because it provides a promising strategy to fabricate structures in a bottom-up way for potential applications in electrical networks, reinforced materials and tissue scaffolds. Whitesides is considered pioneers for the concept of macroscopic self assembly. He assembled the millimeter size objects through minimization of interfacial energy. In 2011, Harada's group reported the macroscopic assembly of hydrogel system through molecular recognition by host host-guest interaction. After that, researchers have established various interactions like electrostatic interaction, DNA hybridization, magnetic interactions etc for self-assembly at macroscopic scale. In order to further promote the research in this area, our group has given the concept of flexible spacing coating on rigid building blocks. However, at this early stage macroscopic supramolecular assembly confronts some main challenges and need to be further addressed.A big challenge is to understand and handle the ubiquitous mis-matching phenomena in many advanced and complex artificial self-assembly processes, among which macroscopic supramolecular assembly is a good example. To clarify whether interactive surface area is the dominant factor for the ordering of the assembled structures, we have utilized the interactive-surface-area dependent macroscopic supramolecular assembly of millimeter cylindrical building blocks of different diameter/height (d/h) ratios with host-guest interactions. Furthermore, we have also employed the coordination chemistry of transition element for further understanding of macroscopic assembly-disassembly behavior. The main objectives of our study were as follows.Firstly, we have proposed the interactive-surface-area-dependent assembly to interpret the effects of interactive surface area on the widely existing mis-matching phenomena in macroscopic supramolecular assembly. By using millimeter cylindrical building blocks as a model system for advanced and complex artificial self-assembly, we have investigated the assembling behaviors of cylinders of different d/h ratios through host-guest interactions and interpreted both kinetic and thermal reasons for different possibility of face-face, face-side and side-side assembled geometries. At low d/h ratios, the collision chances are advantageous for high percentage of face-side forms; with increasing d/h ratios, the thermal stability was dominant to result highly selective face-face assembly.Secondly, we have also developed a new macroscopic assembly-disassembly system based on chemistry of covalent coordination between transition metal neutralized polyelectrolytes and ligand (pyridine-) containing polymer. This switch on-off system was controlled by EDTA, who has remarkable ability to extract the metal ions from the multilayers.