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

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

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

J Org Chem. 2013 Apr 19;78(8):3561-9.

PMID: 23547907

Abstract:

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 (MW) of 25000. We also used competition experiments to determine approximate rate constants for reactions of phenyl radicals with CHO (k = 2 × 10(6) M(-1) s(-1)) and with TFP (k = 2 × 10(8) M(-1) s(-1)).

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP61358256	Bis(4-tert-butylphenyl)iodonium hexafluorophosphate		61358-25-6	Price

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