| dc.description.abstract | Ladder-type conjugated molecules and macromolecules are attractive organic materials with optical and electronic properties suitable for various applications, as a result of their extended π-delocalization and strong intermolecular coupling facilitated by their rigid coplanar structures. This dissertation focuses on the incorporation of ladder-type constitution in aromatic and quinoidal conjugated oligomers and polymers, in order to address the fundamental challenges associated with conjugated organic materials, such as stability and limited delocalization ranges of states or quasi-particles.
This dissertation begins with a brief introduction of ladder-type conjugated structures and quinoidal resonance (Chapter I). Important concepts that are involved in the following chapters are introduced and related challenges are discussed.
Chapter II describes an example of conjugated ladder polymer featuring rigid coplanar backbone and self-complementary intermolecular hydrogen-bonding interactions. To address the low-solubility challenge in the field of ladder polymers, a reversible protection and cleavage strategy is employed, realizing solution-phase characterization and processing. The rigid backbone with strong intermolecular interactions leads to compact aggregation and this ladder polymer demonstrates excellent thermal and chemical stability, showing promising potential as coating materials for harsh environment applications.
In Chapter III, ladder-type constitution is incorporated in a pernigraniline salt-derived system containing quinoidal building blocks. As the fully-oxidized and acid-doped derivative of polyanilines, pernigraniline salt is not well-understood due to their poor stability and configurational uncertainty. Ladder-type constitution is imparted into a series of oligomers to address these issues, demonstrating well-defined configuration and excellent chemical stability after protonation, rendering it possible to reveal the intrinsic electronic and magnetic properties of pernigraniline salt species with quinoidal moieties. A dominant Pauli paramagnetism was observed in the solid state, which indicates the delocalization nature of polarons in the ladder oligomers as a result of extended intramolecular and intermolecular interactions.
Shown in Chapter IV, this design principle is expanded into a macromolecular system as ladder-type polyaniline derivatives. The chemical stability the ladder polymer ensures an unprecedented electrochemical stability of this material under highly oxidative conditions. Interconversions among different redox states have been achieved in a highly reversible and robust manner in both chemical and electrochemical processes. This material is applied in an electrochromic device, showing distinct switches between UV- and near-infrared-absorbing states with a remarkable cyclability and high tolerance to operation voltages.
Overall, this dissertation is to demonstrate the strategy of incorporating ladder-type constitution in aromatic and quinoidal conjugated macromolecules to address challenges in the field of organic electronic materials in both fundamental and application research. Unprecedented properties, including enhanced stability and extended delocalization ranges of states, are investigated in ladder-type conjugated macromolecules, showing their great potential as next-generation electronic active materials. | en |
