Current Search: Johns, Valentine (x)
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Title
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Photochemistry and Applications of Diels-Alder Adducts and Photoacids in Materials Science.
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Creator
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Johns, Valentine, Liao, Yi, Miles, Delbert, Zou, Shengli, Gesquiere, Andre, Su, Ming, University of Central Florida
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Abstract / Description
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Utilizing light as an energy source for reactions has intrigued many chemists. This has led to the development of the principles of photochemistry. The Photo retro Diels Alder (PrDA) reaction is one such system that has potential for use in materials science as well as in the life sciences. However, there was no guide to predict whether a compound could undergo the PrDA reaction, which limits the widespread use of this reaction. Another system is that of photoacids (molecules that release...
Show moreUtilizing light as an energy source for reactions has intrigued many chemists. This has led to the development of the principles of photochemistry. The Photo retro Diels Alder (PrDA) reaction is one such system that has potential for use in materials science as well as in the life sciences. However, there was no guide to predict whether a compound could undergo the PrDA reaction, which limits the widespread use of this reaction. Another system is that of photoacids (molecules that release protons upon irradiation reversibly). Since most fundamental processes involve proton transfer, these types of photoacids have great potential which is yet to be explored. This thesis describes the design and synthesis of various aromatic DA adducts. These adducts were made to undergo the rDA reaction using UV (Ultra-Violet) light. Experimental results showed that the photoreactivity of these adducts depends on the electron-donating ability of the diene component and the electron-withdrawing ability of the dienophile component. In addition, mechanistic study of this reaction revealed the formation of a charge separated intermediate with a singlet excited state. The potential of the PrDA reaction was also explored in two ways. One was by designing isomeric DA adducts from pentacene and TCNE (tetracyanoethylene) which are capable of switching from one isomer to another via a PrDA process. The other way was the design and synthesis of a polymer with an anthracene diketone moeity which could undergo a PrDA reaction to change from an insulator to a semiconductor. Finally, the syntheses of a number of photoacids which not only become acidic upon irradiation but also respond to visible light reversibly have been explored. A rationale has been developed for the design of photoacids with desired photo-induced response. While electron donating and accepting groups in strategic positions help tune the pH; using different combinations of ethanol and water affect the rate of the forward and the backward processes. A photoacid monomer was also incorporated into three photoacid polymers which respond to visible light reversibly, hence promising widespread applications of these photoacids.
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Date Issued
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2012
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Identifier
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CFE0004556, ucf:49235
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Format
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Document (PDF)
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PURL
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http://purl.flvc.org/ucf/fd/CFE0004556
