End-Quenching of Quasiliving Carbocationic Isobutylene Polymerization With Hindered Bases: Quantitative Formation of Exo-Olefin-Terminated Polyisobutylene
Polymers and High Performance Materials
Polyisobutylenes possessing exclusively exo-olefin end groups were created by end-quenching TiCl4-catalyzed quasiliving isobutylene (IB) polymerizations with a hindered base at -60 to -40 degrees C. Polymerizations were initiated from either 2-chloro-2,4,4-trimethylpentane (TMPC1) or 1,3-bis(2-chloro-2-propyl)-5-tert-butylbenzene, in 60/40 hexane/methyl chloride in the presence of 2,6-dimethylpyridine, allowed to reach 98+% isobutylene conversion, and then reacted with either 2,5-dimethylpyrrole, 1,2,2,6,6-pentamethylpiperidine, or 2-tert-butylpyridine for various times ranging from 10 to 170 min. Typical reaction molar concentrations were [IB] = 0.5, [TMPCl] = 0.014, [26Lut] = 0.010, [TiCl4] = 0.083, and [hindered base] = 0.02-0.04 M. In some cases, minor amounts of coupled PIB were produced through reaction of carbenium ions with e.ro-olefin. Coupling was suppressed by higher temperature and lower chain end concentration. 2,5-Dimelhylpyrrole was the most effective quencher under the conditions studied, yielding the most rapid quenching and exhibiting the least tendency toward coupling.
Simison, K. L.,
Stokes, C. D.,
Harrison, J. J.,
Storey, R. F.
(2006). End-Quenching of Quasiliving Carbocationic Isobutylene Polymerization With Hindered Bases: Quantitative Formation of Exo-Olefin-Terminated Polyisobutylene. Macromolecules, 39(7), 2481-2487.
Available at: http://aquila.usm.edu/fac_pubs/2392