Author : Henry D. Castillo
Release : 2020
Genre : Molecular dynamics
Kind : eBook
Book Rating : /5 ( reviews)

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Book Synopsis Self-assembly at Solution/solid Interfaces by : Henry D. Castillo

Download or read book Self-assembly at Solution/solid Interfaces written by Henry D. Castillo. This book was released on 2020. Available in PDF, EPUB and Kindle. Book excerpt: Molecular self-assembly at surfaces offers an efficient route to highly-ordered organic films that can be programmed for a variety of applications. However, the success of these materials depends on the ability to program intermolecular interactions that determine ordering at the surface. We study three systems: alkoxybenzonitriles (ABNs), tricarbazolo triazolophane macrocycles (tricarb), and triazolobenzene oligomers in flexible or macrocycle forms. For each model system, experiments employ a range of molecules in which aspects of molecular structure, especially symmetry and peripheral functionalization, are systematically varied to study the impact of intermolecular interactions on 2D supramolecular structure and to gain a deeper understanding of fundamental assembly mechanisms. The supramolecular assemblies are studied by scanning tunneling microscopy (STM) and molecular dynamic (MD) simulations at the solution/graphite interface. Variations in assembly conditions, including solvent, concentration, and temperature, also provide insight into assembly. ABNs exhibit competitive assembly with solvent that can be controlled with alkyl length. MD simulations on nanosecond timescales provide insight into ABN desorption, re-adsorption, and on-surface processes, and simulations reveal an asymmetry in desorption pathways. Triazolobenzene oligomers can be tuned between tight and loose packing of aromatic cores, the latter being separated by lamellar rows of alkanes. Flexible frameworks assemble more slowly compared to macrocycles due to a large conformational space, but self-assembly can be accelerated by co-solutes and STM perturbation. Tricarb exhibits polymorphism, and tricarb-tricarb hydrogen bonding can be controlled by varying the length and symmetry of peripheral alkanes into various structures including a high-density disordered packing. Variable solvent and peripheral group studies indicate that transitions from disordered to ordered structures involve a solution-mediated annealing pathway. MD simulations reveal solvent insertion between tricarb leading to disordered structures, but these can be sterically blocked by longer alkanes. The discoveries presented in this thesis provide insights into the dynamics and design rules of self-assembly.