Trialkyl Phosphites and Diaryliodonium Salts as Co-initiators in a System for Radical-Promoted Visible-Light-Induced Cationic Polymerization

详细信息    查看全文

• 作者：Thomas W. Nalli ; Lee G. Stanek ; Rebekka H. Molenaar ; Krysia L. Weidell ; Justin P. Meyer ; Brandon R. Johnson ; Timothy T. Steckler ; Jay Wm. Wackerly ; Missy Jo Studler ; Kevin L. Vickerman ; Stephen A. Klankowski
• 刊名：The Journal of Organic Chemistry
• 出版年：2013
• 出版时间：April 19, 2013
• 年：2013
• 卷：78
• 期：8
• 页码：3561-3569
• 全文大小：333K
• 年卷期：v.78,no.8(April 19, 2013)
• ISSN：1520-6904

文摘

Trialkyl phosphites ((RO)₃P) can act as co-initiators for the diaryliodonium-induced cationic polymerization of cyclohexene oxide (CHO) or THF. A radical initiation step is also required, consistent with the essential role of a radical chain reaction of the phosphite with the iodonium salt to form polymerization-starting aryltrialkoxyphosphonium salts (ArP⁺(OR)₃). We used the visible photolysis of phenylazoisobutyronitrile (PAIBN) as the radical initiation step. The presence of multiple fluorine substituents on the phosphite, as in tris(2,2,2-trifluoroethyl) phosphite (TFP), allows polymerization to proceed with a minimal amount of chain transfer from nucleophilic attack by the phosphite. In a typical experiment, a CHO solution of bis(4-tert-butylphenyl)iodonium hexafluorophosphate (0.05 M), TFP (0.1 M), and PAIBN (0.02 M) was illuminated with a 65-W compact fluorescent bulb for 1 h, resulting in a 78% conversion to poly(cyclohexene oxide) with an average molecular weight (M_W) of 25000. We also used competition experiments to determine approximate rate constants for reactions of phenyl radicals with CHO (k = 2 脳 10⁶ M^鈥? s^鈥?) and with TFP (k = 2 脳 10⁸ M^鈥? s^鈥?).