Single-walled carbon nanotubes: Induced decomposition of peroxides and non-covalent encapsulation into water-soluble PEG-eggs
Abmayr, David William, Jr
Engel, Paul S.
Doctor of Philosophy thesis
This thesis presents two studies aimed of furthering the understanding of single-walled carbon nanotube (SWNT) chemistry for potential applications in composite and biological systems. In composite systems, SWNTs are used as structural members, and bis-acyl peroxides are frequently used as reaction initiators to cure the surrounding matrix. The behavior of the peroxide is often critical to the performance of the final composite. In this study, SWNTs are shown to induce the decomposition of a series of bis-acyl peroxides by single electron transfer. Four bis-acyl peroxides are evaluated for decomposition rate in the presence of SWNTs via iodometry. The resulting SWNTs are analyzed for functionalization by Raman microscopy and X-ray Photoelectron Spectroscopy (XPS). Benzoyl peroxide (BP), p-methoxybenzoyl peroxide (pMBP), phthaloyl peroxide (PhP), and trifluoroacetyl peroxide (TFAP) have known decomposition characteristics and known sensitivities to electron sources. This study demonstrates that all four peroxides undergo induced decomposition in the presence of SWNTs. Of the four, phthaloyl peroxide exhibits the greatest increase, followed by TFAP, BP, and pMBP. This study also demonstrates that all but TFAP functionalize the SWNTs. The decomposition data may be used to design improved composite systems. In aqueous solution, the ability of SWNTs to heat up upon exposure to radiofrequency energy gives them potential uses in biological systems. SWNTs are not soluble alone in aqueous solution, so one approach is to use amphiphilic triblock copolymers to capture and isolate SWNTs in water. This study addresses the difficulties encountered in synthesizing these polymers reproducibly and controllably. Presented here are modifications to the Atom Transfer Radical Polymerization (ATRP) method that not only enable the reproducible synthesis of these triblocks, but also enable them to be made in a highly controlled manner with specific block lengths. The SWNTs encapsulated by the polymers made through this new approach are shown not only to retain their fluorescence but also to demonstrate fluorescence on par with the best surfactants in current use. These structures are expected to provide a new entry into the use of nonfunctionalized SWNTs in biological systems such as radiofrequency heating for the destruction of cancer cells.