Date of Award

8-2008

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Polymer and Fiber Science

Advisor

Gregory, Richard V

Committee Member

Ellison , Micheal

Committee Member

Lickfield , Gary

Committee Member

Tessema , Grubre

Abstract

ABSTRACT


A series of bis(3,4-ethylenedioxythiophene)-thiophene derivatives (BEDOT-Ts) and bis(3,4-ethylenedioxythiophene)-benzene derivatives (BEDOT-Bs) monomers were electrochemically polymerized onto glassy carbon or ITO-coated glass electrodes. Cyclic voltammetry (CV), infrared (IR), UV-vis-NIR and photoluminescence (PL) spectroscopy were employed to investigate and characterize properties of resulting polymers. dc-conductivities of these polymers were measured by the four-point probe method.
Cyclic voltammetry studies show that the redox half potentials of PBEDOT-3BT, PBEDOT-3OT, PBEDOT-3TBS and PBEDOT-3MPT are -290, -297, -325 and -284 mV versus Ag/Ag+, respectively. The redox half potentials of PBEDOT-TOL, PBEDOT-BOB and PBEDOT-FB are -130, -147 and -327 mV vs. Ag/Ag+, respectively, and a bit higher than that of PBEDOT-Ts. Moreover, the large potential plateau indicates that PBEDOT-Ts and PBEDOT-Bs are stable over a broad potential window.
All polymers exhibit electrochromism and a spectrum of colors in the undoped state, ranging from deep-purple for PBEDOT-3BT and PBEDOT-3OT to reddish for PBEDOT-FB, and blue in the doped state. In addition, these polymers show photoluminescence behavior and their PL are in the orange and red regions.
IR spectroscopy showed that the polymerization should take place at the -position of the EDOT ring, with no opening of the central ring. UV-vis-NIR spectra showed the characteristic of free carrier tail for all polymers in the doped state, and one broad peak in the undoped state that is assigned to the * transition. The optical bandgaps, obtained from the onset of the * transition in the undoped state of these polymers range from 1.65 to 1.85 eV with moderate dc conductivities ranging from 15 to 30 S/cm in the doped state.
PBEDOT-Ts tend to be stable in the intermediate form while PBEDOT-Bs are stable in both the doped and undoped states. The stability, moderate conductivity, luminescence properties, as well as electrochromic behavior of these polymers make them good candidates for optoelectronic materials. abstract is a succinct statement of the significant contents of the manuscript and the value and relevance of the study.

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