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Optical and electronic properties of functional polythiophenes

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Title: Optical and electronic properties of functional polythiophenes
Author: Kunz, Tamara Katherine
Degree Doctor of Philosophy - PhD
Program Chemistry
Copyright Date: 2009
Publicly Available in cIRcle 2010-12-31
Abstract: The synthesis and characterization of a series of functionalized head-to-tail regioregular poly-3-alkylthiophenes are reported. The influences of the structure and functional groups on the optical and electronic properties are investigated with NMR, absorption, emission and infrared spectroscopy, gel permeation chromatography, and cyclic voltammetry. A regioregular poly-3-alkylthiophene (Poly-1) was synthesized via Grignard Metathesis polymerization conditions. Poly-1 contains bromide groups as sites of latent reactivity along the polymer backbone through which additional reactions were carried out post-polymerization. The bromide was converted to an azide group (Poly-2) which was further functionalized via Click chemistry with a variety of functional groups. Click chemistry was carried out using the Huisgen 1,3-dipolar cycloaddition reaction. Post-polymerization functionalization of Poly-2 provided a facile method for preparing a variety of related functional polymers, each with identical average chain length, average polydispersity and average distribution of monomers. Preparation of Poly-3a, -3b, and -3c, demonstrated the utility of the Click reaction for modifications with a variety of functional groups. A series of poly-3-alkylthiophene analogs (Poly-1 - Poly-11) were characterized by absorption and emission spectroscopies and the spectra were found to be dependant on regioregularity along the polymer backbone. The UV-vis absorption maxima, varied with the percentage of head-to-tail couplings in relation to the extent of conjugation. The series of dithienylethene functionalized oligo- (71) and polymer analogs (Poly-4, Poly-7 and Poly-11) displayed fluorescence quenching capabilities upon photoinduced ring closing of the dithienylethene moiety via energy transfer. The extent of quenching was determined to be dependent on both the length and structure of the backbone. Extended conjugation contributed to amplified fluorescence quenching as observed by complete fluorescence quenching of Poly-4. The functionalization of the Poly-2 with the stable free nitroxide radical 2,2,6,6- tetramethylpiperdine-1-oxyl is described. The resulting polymer, Poly-12, was characterized with cyclic voltammetry and IR spectroscopy. Electrochemical deposition of thin films of Poly-12 onto various working electrodes is described. The thin films were investigated for potential charge storage via galvanostatic charge/discharge cycles. IR spectroscopy revealed that the nitroxide radical had sensitized the polythiophene backbone to oxidation, resulting in irreversible damage to the polymer and reduced charge storage capacity.
URI: http://hdl.handle.net/2429/17459

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