Date of Award
Chemistry and Biochemistry
Conjugated polymer, Dynamic interactions, Internet of things, Organic field-effect transistor, Semiconductor, Stretchable
The development of materials that can stretch while remaining conductive has generated significant research interest. The push for the development of these materials is due to their potential for cheaper, more durable electronics with the new functions (stretchability and healability) and form factors required for the next generation of wearable and skin-inspired electronics. Polymeric semiconductors have emerged as prime candidates for the development of these materials, due to their π-delocalized network which makes them conductive, their synthetic versatility, and their intrinsic mechanical properties. Furthermore, their ability to be solution processed provides an avenue for printing, roll-to-roll, and large area solution processing. Though, the combination of stretchability and good electronic properties has often proven difficult to achieve, given the apparent competition between mechanical compliance and electrical conductivity. Consequently, this dissertation focuses on strategies to synthesize novel conjugated polymers with the ability to maintain good charge transport while being manipulated by strain, specifically through the incorporation of dynamic interactions.
A review of the recent literate is presented in chapter 1, with a particular focus on intrinsically/molecularly stretchable and healable conjugated polymers, as well as a brief overview of other extrinsic methods of imparting stretchability and healability. Following in chapter 2 is a study of the effect of amide-containing solubilizing sidechains on the self-assembly and electronic properties of diketopyrrolopyrrole (DPP)-based polymers, emphasizing the maintenance of electronic properties at high percentage incorporation as compared to other systems that make use of conjugation-break spacers. Chapter 3 investigates the mechanical properties of these materials through characterization of the thin-film morphology and its relative crystallinity, strain at failure, chain dynamics under strain, and healability.
Many other systems that make use of noncovalent interactions do so intermolecularly. Accordingly, in chapter 4, we examine the effect of an electrostatic nitrogen-sulfur conformational lock directed intramolecularly along the backbone, rather than intermolecularly between sidechains. Investigation of conformational lock is particularly interesting because it improves the electronic properties by brining the π-orbital network into greater alignment. Chapter 5 presents a comparison of the two modes of interaction investigated in the previous chapters – intermolecular and intramolecular bonding. Using the materials in chapter 4 as a starting point, we changed the nitrogen-sulfur interaction into a stronger intramolecular hydrogen-bonding interaction along the backbone and compared it to an entirely intermolecular analogue. Finally, chapter 6 presents a conclusion and insights into future work.
Ocheje, Michael Udunyi, "Dynamic Interactions in Semiconducting Polymers; New Materials for Soft Electronics with Biomimetic Properties" (2022). Electronic Theses and Dissertations. 8799.