title: Trialkyl phosphites and diaryliodonium salts as co-initiators in a system for radical-promoted visible-light-induced cationic polymerization.
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)).
authors.affiliation: Chemistry Department, Winona State University, Winona, Minnesota 55987-5838, USA. tnalli@winona.edu
authors.forename: Thomas W
authors.initials: TW
authors.lastname: Nalli
authors.forename: Lee G
authors.initials: LG
authors.lastname: Stanek
authors.forename: Rebekka H
authors.initials: RH
authors.lastname: Molenaar
authors.forename: Krysia L
authors.initials: KL
authors.lastname: Weidell
authors.forename: Justin P
authors.initials: JP
authors.lastname: Meyer
authors.forename: Brandon R
authors.initials: BR
authors.lastname: Johnson
authors.forename: Timothy T
authors.initials: TT
authors.lastname: Steckler
authors.forename: Jay Wm
authors.initials: JW
authors.lastname: Wackerly
authors.forename: Missy Jo
authors.initials: MJ
authors.lastname: Studler
authors.forename: Kevin L
authors.initials: KL
authors.lastname: Vickerman
authors.forename: Stephen A
authors.initials: SA
authors.lastname: Klankowski