ISSN:
0887-624X
Keywords:
isobutylene polymerization
;
living carbocationic
;
conventional carbocationic
;
proton trap
;
mechanism
;
kinetics
;
Chemistry
;
Polymer and Materials Science
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The effect of the proton trap, 2,6hyphen;di-tert-butylpyridine (DtBP), on the polymerization of isobutylene (IB) induced by the “HX”/TiCl4 (“HX” = protoic impurity) intiating system has been studied. Significantly, in the presence of a large (∼ 40 molar) excess of DtBP relative to “HX”, free proton-induced chain transfer-dominated conventional IB polymerization is converted to living polymerization. In the absence of the proton trap the kinetics are dominated by rapid proton-induced processs which overwhelm the relatively slower living polymerization. These investigations also led to a quantitative assessment of the concentration of initiating species: [“HX”] = 1.46 × 10-4 mol/L. The polymerizations are first-order in monomer and the apparent rate constants of propagation drop precipituously with increasing DtBP concentration until a constant low value is reached. The rate of formation of propagating living chains has been expressed quantitatively. Chain transfer is bimolecular and first order in monomer, and kinetic investigations led to a quantitative description of the effect of proton trap concentration on the apparent first order chain transfer constant. The results have been explained in terms of a simple mechanistic scheme. © 1996 John Wiley & Sons, Inc.
Additional Material:
6 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/pola.1996.839
