Single-walled carbon nanotubes (SWNTs) are envisioned as one of the most promising materials for next-generation electronic devices such as field-effect transistors, photovoltaics, new power sources and bio/chemical sensors. In particular, solution processable SWNT networks are of great interest for flexible and stretchable electronics. However, most of these applications specifically require pure semiconducting (sc-) or metallic (m-) SWNTs. However, large scale synthetic methods for SWNTs always produce a mixture of semiconducting and metallic carbon nanotubes. In recent years, several biochemical separation techniques such as DNA assisted separation, density gradient ultracentrifugation, and gel chromatography techniques have been utilized to separate semiconducting and metallic SWNTs. Although these methods can be used for sorting SWNTs according to their chiralities, they are either time-consuming or not easily scalable. In addition, the supramolecular functionalization of SWNTs with conjugated polymers has received a great deal of attention due to its capability to extract sc-SWNTs via simple sonication and centrifugation steps within a few hours. Furthermore, π-conjugated polymers can be modified by suitably changing monomers and/or comonomers, and it is also easy to control molecular weight and solubility of resulting polymers in organic solvents and aqueous media. There is also the possibility for selectively extracting specific chirality (n, m) nanotubes using specifically designed macromolecular structures. Except for its application to the separation of SWNTs, the supramolecular complexes of π-conjugated polymer and SWNTs have potential applications in many research areas such as new composite materials.
After a brief overview of the current work related to the investigation of the supramolecular interaction between various conjugated polymers and SWNTs (chapter 1), synthesis of a series of different types of fluorene-based conjugated copolymers and their supramolecular complex formation properties with SWNTs are described (chapter 2, 3, 4, 5 and 6). In order to understand the effect of conjugated polymer backbone and side-chain structure on formation of supramolecular complexes with SWNTs, several crucial factors were investigated by: (1) altering the polymer backbone composition; (2) introducing different solubilizing (functional) groups while the polymer backbone remains the same; (3) changing the side-chain functional groups, and (4) introducing different polymer repeat units with varying physical and chemical properties. The experimental results indicated that all of the resulting polymer-SWNTs complexes possess excellent (or moderate) solution stability in organic solvents such as tetrahydrofuran (THF), toluene, and xylene. It was also demonstrated that the interaction between the conjugated polymers and SWNTs is strongly influenced by polymer structure; even minor changes on side-chains have a significant effect on the selectivity of the polymers in dispersing specific SWNT structures.
This investigation highlights the potential importance of incorporating different types of heterocyclic aromatic rings (electron rich or electron poor), and introducing side chains with varying electronic and geometric structure on selective solubilization of SWNTs. Polymer molecular weight and solvent properties also strongly influence the π-conjugated polymer assisted dispersion of specific chirality SWNTs. Although some progress has been made, the search for a conjugated polymer that selectively solubilizes specific SWNT chiralities on large scale remains a challenge. / Thesis / Doctor of Philosophy (PhD)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/20443 |
| Date | 14 September 2016 |
| Creators | Muhetaer, Yimiti |
| Contributors | Adronov, Alex, Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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