Mechanism of Photoinitiated Free Radical Polymerization by Thioxanthone鈭扐nthracene in the Presence of Air

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• 作者：Demet Karaca Balta ; Nergis Arsu ; Yusuf Yagci ; Arun K. Sundaresan ; Steffen Jockusch ; Nicholas J. Turro
• 刊名：Macromolecules
• 出版年：2011
• 出版时间：April 26, 2011
• 年：2011
• 卷：44
• 期：8
• 页码：2531-2535
• 全文大小：777K
• 年卷期：v.44,no.8(April 26, 2011)
• ISSN：1520-5835

文摘

The mechanism of formation of initiating radicals for free radical polymerization by the thioxanthone鈭抋nthracene (TX-A) photoinitiator was investigated by laser flash photolysis, fluorescence and phosphorescence spectroscopy, and polymerization studies. The proposed mechanism of photoinitiation involves photoexcitation of TX-A and quenching of triplet excited states of TX-A by molecular oxygen to generate singlet oxygen. Singlet oxygen reacts with the anthracene moiety of TX-A to form an endoperoxide. The endoperoxide intermediate was isolated and characterized by MS and ¹H NMR. The endoperoxide undergoes photochemical or thermal decomposition to generate radicals which are able to initiate free radical polymerization. A significant deuterium effect on the polymerization rates using CDCl₃ and CHCl₃ as solvents confirmed the involvement of singlet oxygen in the initiation process.