- Trialkyl phosphites and diaryliodonium salts as co-initiators in a system for radical-promoted visible-light-induced cationic polymerization(1)
-
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 × 106 M-1 s-1) and with TFP (k = 2 × 108 M-1 s-1).
- Nalli, Thomas W.,Stanek, Lee G.,Molenaar, Rebekka H.,Weidell, Krysia L.,Meyer, Justin P.,Johnson, Brandon R.,Steckler, Timothy T.,Wackerly, Jay Wm.,Studler, Missy Jo,Vickerman, Kevin L.,Klankowski, Stephen A.
-
p. 3561 - 3569
(2013/06/04)
-
- THE THERMOLYTIC DECOMPOSITION OF ACYCLIC PHOSPHORANES
-
The thermolytic decomposition of acyclic phosphoranes, ArnP(OCH2CF3)5-n in aprotic media has been shown by kinetic studies to proceed via rate-limiting ionization of the phosphoranes.Activation parameters, deuterium isotope effects, solvent effects and ρ-values (for n = 3 and n = 1) support this concept which is consistent with the observed rate-sequence of n = 3> n = 2 > n = 1 > n = 0.Key words: Phosphoranes, thermolysis, kinetics, mechanism.
- Lowther, Nicholas,Crook, Polly,Hall, C. Dennis
-
p. 195 - 204
(2007/10/02)
-
- CONCERNING THE FORMATION, HYDROLYSIS AND THERMOLYSIS OF ACYCLIC PHOSPHORANES
-
Kinetic data on the formation, hydrolysis and thermolysis of acyclic phosphoranes is reported and the mechanism of each reaction is discussed.
- Lowther, Nicholas,Crook, Polly,Hall, Dennis
-
p. 405 - 408
(2007/10/02)
-
- A Duality of Mechanism in the Hydrolysis of Acyclic Phosphoranes
-
Acyclic phosphoranes, ArnP(OR)5-n with n=0-3 are shown to hydrolyse in neutral conditions by SN1 (P) mechanism for n=1,2, and 3 but by an SN2 (P) or addition-elimination mechanism for n=0; this is analogous to the classical SN1 vs.SN2 mechanisms observed for solvolysis reactions at tetrahedral carbon.
- Lowther, Nicholas,Hall, C. Dennis
-
p. 1303 - 1305
(2007/10/02)
-