Polyisobutylenes possessing exclusively exo-olefin end groups were created by end-quenching TiCl 4 -catalyzed quasiliving isobutylene (IB) polymerizations with a hindered base at -60 to -40 °C. Polymerizations were initiated from either 2-chloro-2,4,4-trimethylpentane (TMPCl) 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, [TiCl 4 ] ) 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 exo-olefin. Coupling was suppressed by higher temperature and lower chain end concentration. 2,5-Dimethylpyrrole was the most effective quencher under the conditions studied, yielding the most rapid quenching and exhibiting the least tendency toward coupling.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.