Date of Degree

2-2016

Document Type

Dissertation

Degree Name

Ph.D.

Program

Chemistry

Advisor

Ralf M. Peetz

Committee Members

Alexander Greer

Krishnaswami Raja

Subject Categories

Polymer Chemistry

Keywords

ADMET, CONJUGATED POLYMERS, DONOR-ACCEPTOR POLYMERS, SYNTHESIS, CHARACTERIZATION, POLYMERS

Abstract

This doctoral thesis is focused on the novel and facile synthesis and characterization of segmented conjugated polymers featuring various electro-optically active segments, with or without heteroatom linkages. The polymers were synthesized, via acyclic diene metathesis (ADMET) using ruthenium-based Grubbs-type catalysts. All products are soluble, and have a well-defined all-trans microstructure without defects. Some of the polymers were also synthesized via Suzuki polycondensation for comparison purposes. All monomers utilized were designed and synthesized in the laboratory.

Segmented conjugated polymers have received a great deal of attention in organic electronics, such as organic light emitting-diodes, organic field-effect transistors and organic solar cells due to that fact they are more flexible, lightweight and processable than their inorganic counterparts. ADMET allowed us access to luminescent conjugated polymers exhibiting different emission characteristics by systematically varying electro-optically active segments in the polymer backbone. The effects of alternating segments (incl. donor-acceptor systems), directly linked and bridged by heteroatoms or vinylene groups, were studied with regard to opto-electronic properties of the polymers. Characterizations included UV-vis, fluorescence spectroscopy, and cyclic voltammetry. Si was found to effectively disrupt the π-conjugation resulting in a well-defined blue emission. The HOMO-LUMO energy levels could be tuned by careful selection of aromatic segments in the polymer backbone. E.g. systems with alternating functionalized phenylene vinylene and benzothiadiazole segments exhibited strong electronic interactions between segments, resulting in broad absorptions and lower HOMO-LUMO band gaps, which are important for higher power conversion efficiencies in solar cells. The experimental results obtained were consistent with calculated data obtained from density functional theory (DFT) calculations

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