2-Mercaptothioxanthone as Sensitizer and Coinitiator for Acylphosphine Oxide Photoinitiators for Free Radical Polymerization

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• 作者：Sevnur Keskin ; Steffen Jockusch ; Nicholas J. Turro ; Nergis Arsu
• 刊名：Macromolecules
• 出版年：2008
• 出版时间：July 8, 2008
• 年：2008
• 卷：41
• 期：13
• 页码：4631 - 4634
• 全文大小：341K
• 年卷期：v.41,no.13(July 8, 2008)
• ISSN：1520-5835

文摘

The initiation efficiencies of photoinitiators for free radical polymerization, 2,4,6-trimethylbenzoyldiphenylphosphine oxide (TMDPO) and bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide (BAPO), are enhanced by addition of mercaptothioxanthone (TX-SH) to the initiator formulation. The additive TX-SH combines the benefits of a triplet sensitizer (enhanced light absorption) and thiol functionality (reduced oxygen inhibition). On the basis of polymerization studies, laser flash photolysis, fluorescence, and phosporescence, the following mechanism is proposed: most of the light is absorbed by TX-SH to generate ³(TX-SH)*, which transfers its energy to TMDPO and BAPO followed by α-cleavage to produce the initiating radicals. In addition, excellent polymerization yields were observed in air-saturated solutions when TX-SH was added. With the addition of TX-SH to initiation formulations, the inhibition due to oxygen is reduced, probably by the generation of reactive thiyl radicals by hydrogen abstraction of inactive peroxyl radicals from the thiol functionality.