Doctor of Philosophy (PhD)
This investigation focused on the analytical characterization of poly(3-hexylthiophene), a heterocyclic conducting polymer system, with an overall objective of elucidating the effects that the experimental conditions during chemical oxidation using iron(III) chloride as an oxidant impart on the structure of the resulting polymers. Poly(3-alkylthiophene)s are extensively studied materials due to their high electrical conductivities and unique optical properties that make them extremely valuable for use in contemporary technological applications and devices. Specifically, the aim of this research was to determine the dependence of structural characteristics, such as endgroups, molecular weights, and regioregularities, on the solvent employed for the reaction and the temperature the reaction was performed. Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-ToF-MS) was used to characterize the endgroup additions to and obtain molecular weight data about poly(3-hexylthiophene) formed using different experimental conditions. The regioregularity of the materials was evaluated by means of 1H-NMR. Also, average molecular weights and molecular weight distributions were gathered by analytical and semi-preparative size-exclusion chromatography. In this study it was demonstrated that the physical properties of the solvents employed for chemical oxidation, such as polarity and Lewis acidity and basicity, imparted markedly different structural characteristics to the resulting polymer. It was also shown that the temperature at which the reactions were performed dramatically impacted the extent of chlorination to and the regioregularity of the resulting polymers. Finally, this study revealed for the first time that multiply-charged ion species are formed during the MALDI-ToF-MS analysis of poly(3-alkylthiophene)s and that the presence of these species dramatically affects the accurate determination of molecular weight information for these materials by MALDI-Tof-MS analysis. Chemical oxidative polymerization remains the most popular and wide-spread method for the preparation of P3ATs, due to the method’s affordability, ease, and ability to form large yields of high mass polymer. Therefore, the ability to utilize this synthetic route with a better understanding as to the effects of the experimental conditions−which may be employed in order to augment the materials characteristics−is of utmost importance. The work presented in this Dissertation has demonstrated that through the proper selection of solvent, and/or adjustment to temperature, this simple and convenient synthetic method can be employed to modify the properties of the resulting P3ATs.
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Solfiell, Warren James, "Structure-Function Relationships in Poly(3-hexylthiophene)s Formed via Manipulation of Oxidative Coupling Routes" (2011). LSU Doctoral Dissertations. 1434.
McCarley, Robin L.