Latently-reactive conjugated polymer-coated single-walled carbon nanotubes / Single-walled carbon nanotubes (SWNTs) are intensely investigated nanomaterials that exhibit intriguing physical and optoelectronic properties. Although SWNTs are highly regarded in terms of their potential societal impact, commercialization of SWNT applications has been dampened by the difficulty in SWNT processability and purification. Current commercially viable carbon nanotube syntheses produce complex mixtures of metallic and semiconducting SWNTs, as well as amorphous carbon and metal catalyst particles. Furthermore, the ability to decorate carbon nanotube surfaces to modulate their properties is non-trivial, especially if concurrent preservation of optoelectronic properties is desired. To date, the issues of SWNT solubilization, sorting, and functionalization have been approached in a piecemeal fashion. Conjugated polymers, which are macromolecules that possess extended π-systems, have the potential to address all of these issues simultaneously. In my Thesis, I explore conjugated polymer structures to investigate (i) factors that influence dispersion selectivity, and (ii) the decoration of polymer-SWNT complexes by incorporating reactive moieties into the polymer structure.
The work presented in this Thesis begins by examining the ability of conjugated polymers to sort SWNTs. To date, the selective dispersion of metallic SWNTs is unrealized. In Chapter 2, I examine the effect of the electronic nature of the conjugated backbone on the selective dispersion of SWNTs by preparing SWNT dispersions pre- and post-methylation of a pyridine-containing conjugated polymer. In doing so, I prepare a series of polymers with identical degrees of polymerization and dispersity (to minimize extraneous selectivity factors) and find that electron rich π-systems disperse only semiconducting SWNTs, while electron poor π-systems disperse relatively more metallic SWNTs. In Chapter 3, I challenge the conventional wisdom that complete backbone conjugation is required to selectively disperse semiconducting SWNTs by introducing non-conjugated linkers into the polymer backbone and demonstrating that nanotube sorting is still possible.
I next examine conjugated polymers as tools that can simultaneously sort SWNTs and impart reactivity to the polymer-SWNT complex, while preserving SWNT optoelectronic properties. In Chapter 4, I incorporate azides into polyfluorene side chains and perform solution-phase Strain-Promoted Azide-Alkyne Cycloaddition (SPAAC). I show that the polymer-SWNT complex can be rapidly decorated with strained cyclooctyne derivatives, and that only pre-clicked polymer enables for sorting of semiconducting SWNTs. The sorted SWNT population can then be made water soluble post-SPAAC, enabling for the study of SWNT emission in solvents with very different polarity. In Chapter 5, I examine the reactivity of azide-containing polymer-SWNT thin films and show that thin film properties can be drastically altered. Interfacial chemistry enables for the spatially-resolved patterning of a Janus polymer-SWNT thin film containing both hydrophilic and hydrophobic regions. In Chapter 6, I devise a system to perform aqueous solution-phase chemistry on the polymer-SWNT complex. The water soluble polymer-SWNT complex allows for functionalization of the hydrophobic SWNT scaffold with polar and charged molecules. Clicking an acidochromic switch onto the polymer-SWNT surface enables for control over the SWNT emission properties.
Lastly, in Chapter 7 I develop a conjugated polymer whose backbone can be functionalized using visible light. The visible-light mediated photoclick coupling of a conjugated polymer backbone enables for rapid polymer modification and is the first example of spatially-resolved conjugated polymer backbone functionalization. / Thesis / Doctor of Philosophy (PhD) / Carbon nanotubes are cylindrical shells of carbon that possess fascinating physical, optical, and electrical properties. Commercial syntheses of carbon nanotubes produce complex mixtures of impure material, and raw carbon nanotube samples further suffer from insolubility. A grand challenge preventing commercialization of carbon nanotube applications is simultaneously solubilizing, sorting, and functionalizing carbon nanotube structures while avoiding damage to the nanotube properties. To date, these issues have been tackled in a piecemeal fashion. In my Thesis, I explore conjugated polymer coatings as a solution to address these problems all at once. I investigate how modifying conjugated polymer structure can (i) influence carbon nanotube purification and (ii) produce latently-reactive polymer-nanotube complexes that can be used to decorate carbon nanotubes without damaging nanotube properties.
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/24328 |
| Date | January 2019 |
| Creators | Fong, Darryl |
| Contributors | Adronov, Alex, Chemistry and Chemical Biology |
| Source Sets | McMaster University |
| Language | English |
| Detected Language | English |
| Type | Thesis |
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