| dc.description.abstract | Intramolecular hydrogen bonding as a means of conformational control represents a promising strategy for manipulating a wide range of properties of organic π-conjugated molecules. The past few decades saw significant advances and developments in the field of organic π-conjugated materials, but there still remains significant knowledge gaps in the design principles associated with conformation. This dissertation focuses on the control of molecular conformation of π-conjugated molecules and macromolecules using hydrogen bonds.
This work begins with a brief introduction of π-conjugated materials involving hydrogen-bond conformational locks in Chapter I. It also outlines the importance of theoretical simulations in this field. Specific challenges in this field are identified in order to discuss the breakthroughs in employing hydrogen-bonds to achieve high-performing electronic materials.
Chapter II demonstrates the use of density functional theory computational method as a means of screening molecular designs, corroborating experimental data, and mechanistically investigating unprecedented results. Particularly important methods include the investigations into the thermodynamics of torsional rotation for strategic structural comparisons, and also the correlation of simulated electrostatic potential maps to experimental investigations in intermolecular interactions.
Reaching beyond the theoretical realm, Chapter III discusses the experimental integration of pre-organized hydrogen bond strategy upon diazaisoindigo building blocks, involving synthesis and characterization. As a result of the robust intramolecular hydrogen bonds, thermally unyielding molecular conformations were achieved, elucidated not only by theoretical resources, but through thermal analysis and variable temperature toughness experiments. Facile syntheses of these materials allowed for the systematic study from fundamental optical and electronic experiments to applications in organic electronics.
In this context, Chapter IV describes several molecular engineering and process engineering approaches to optimize solubility, thin-film processibility, solid state packing, and ultimately electronic device performances of π-conjugated model compounds. The robust hydrogen-bonds aided in thin-film processing and, consequently, led to the fabrication of organic field-effect transistor devices that show hole transport mobility up to 0.27 cm2V−1s−1. Furthermore, the measured organic field-effect transistor performances established clear correlations between rudimentary chemical properties and bulk organic electronic material engineering principles.
Last but not least, attempts at extending these hydrogen-bond-bridged π-conjugated structures into macromolecular backbone is detailed in Chapter V. Synthetic challenges illuminated the importance of frontier molecular orbital energy tuning for palladium-catalyzed cross-coupling reactions and the necessity of adequate polymer solubility. To overcome these hurdles, new polymer building blocks were developed to ameliorate these concerns for the future development of H-bond-bridged π-conjugated materials.
In summary, this dissertation describes a series of approaches to elucidate the structure-property relationships of hydrogen-bond-centered conformational control towards the performance of π-conjugated materials through (i) density functional theory exploration of π-conjugated molecules, (ii) installation of hydrogen bond conformational locks on these materials through pre-organized bridging moieties, (iii) and effective molecular and process engineering for use in the fabrication of functioning organic electronic devices. | |
