The ability to control nanoscale morphology and molecular organization in organic semiconducting polymer thin films is an important prerequisite for enhancing the efficiency of organic thin-film devices, including organic light-emitting and photovoltaic devices. The current top-down paradigm for making such devices is based on utilizing solution-based processing (e.g. spin-casting) of soluble semiconducting polymers. This approach typically provides only modest control over nanoscale molecular organization and polymer chain alignment. A promising alternative to using solutions of pre-synthesized semiconducting polymers pursues instead a bottom-up approach to prepare surface-grafted semiconducting polymer thin films by surface-initiated polymerization of small-molecule monomers. This dissertation mainly focuses on development of an efficient method to prepare semiconducting polymer thin films utilizing surface-initiated Kumada catalyst transfer polymerization (SI-KCTP). In chapter 2, we describe SI-KCTP with a new Ni(II) external catalytic initiator to prepare polythiophene (PT) thin films. We provided evidence that the surface-initiated polymerization occurs by the highly robust controlled (quasi-living) chain-growth mechanism. Extensive structural studies of the resulting thin films revealed detailed information on molecular organization and the bulk morphology of the films, and enabled further optimization of the polymerization protocol. Achieving such a complex mesoscale organization is virtually impossible with traditional methods relying on solution processing of pre-synthesized polymers. In addition to controlled bulk morphology, uniform molecular organization and stability, unique feature of SI-KCTP is that it can be used for the preparation of large-area uniformly nanopatterned polymer thin films. This was demonstrated using combination of particle lithography and surface-initiated polymerization.
We expanded scope of the surface-initiated polymerization towards all-conjugated diblock copolymer (polythiophene-b-poly(para-phenylene)) thin films, which is described in chapter 3. In addition to the preparation of such films, we carried out detailed structural studies and investigated optoelectronic characteristics of the films.
In chapter 4, we studied using SI-KCTP to prepare poly(3,4-ethylenedioxithophene) (PEDOT) thin films. PEDOT is a practically important highly conductive conjugated polymer. Our investigation of the properties of a surface-confined PEDOT film revealed that, after doping with iodine, the film became highly conductive, with conductivity comparable to that of inorganic semiconductors. Therefore, surface-confined PEDOT films may find applications in replacing traditional inorganic electrode for the fabrication of flexible organic electronics.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-07112016-135402 |
| Date | 01 August 2016 |
| Creators | Youm, Sang Gil |
| Contributors | Nesterov, Evgueni, Garno, Jayne, Spivak, David, Kato, Naohiro |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-07112016-135402/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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