Synthesis And Characterization Of Pi Conjugated Polymers Utilizing A B Monomers

Author : Venkataramanan Seshadri
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (119 download)

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Download or read book Pi-conjugated Polymers: Synthesis and Application in Devices written by Venkataramanan Seshadri and published by . This book was released on 2005 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The first part of the work embodied in this thesis is towards modifying the electronic band-gap of conjugated polymers consisting of thieno[3,4- b]thiophene as one of the repeat units. Two different approaches were undertaken to prepare copolymers of thieno[3,4-b]thiophene in order to accomplish this. First, a simple simultaneous electropolymerization of two monomers from a solution mixture, and second, an oligomeric approach, wherein an oligomer of thiophene and thieno[3,4-b]thiophene with cyanovinylene spacer units was electrochemically polymerized. Several electroanalytical and spectroscopic techniques were used to characterize these polymers. The major part of the thesis is focused on the electrochromic properties of conjugated polymers both in liquid and solid-state electrochemical cells. Several polymers reported in literature were re-evaluated on the basis of its photopic transmissivity. It is necessary that the contrast in a device is more pronounced at wavelengths, wherein the human eye is most sensitive at a given time of the day. At the same time, it is also important to take into account that the eye is sensitive to a broad spectral range. Hence, this photopic approach is very essential in understanding how the intensity of light can be controlled using electrochromic windows. Furthermore, the optical switchability of solid-state electrochromic windows were also studied. Several issues, such as electrodeposition onto indium doped tinoxide (ITO) surfaces with areas ≥ 30cm2, device stability were addressed during the course of this research. The photopically weighted contrast of the device as a whole was found to be enhanced using derivatives of 3,4-propylenedioxythiophene, belonging to the 3,4-alkylenedioxythiophene family. Finally, new device architecture was studied, wherein very low band-gap conjugated polymer with little/no visible electrochromism was used as the ion-storage layer in a dual polymer configuration. Colorimetric analysis of these devices was compared with the earlier devices incorporating a high band-gap anodically coloring conjugated polymer and low band-gap cathodically coloring polymer. These devices were found to be switching between a deep blue to a sky blue, which is a neutral color, as opposed to deep blue to yellow in the earlier configuration. Yellow filter is known to alter the way colors are perceived by the human eye.