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.

Quasiliving isobutylene polymerization initiated by 2-chloro-2,4,4-trimethylpentane/TiCl4/2,6-dimethylpyridine in 60/40 n-hexane/methyl chloride at −70 °C was allowed to reach 98+% monomer conversion and then reacted with N-methylpyrrole. All polyisobutylene (PIB) chains alkylated the N-methylpyrrole ring to form a mixture of 46% 2-PIB−N-methylpyrrole and 54% 3-PIB−N-methylpyrrole. GPC indicated the absence of coupled PIB, confirming that exclusively monosubstitution had occurred. Complete 1H and 13C NMR chemical shift assignments were made for both isomers. The product was converted exclusively to mixed 2- and 3-PIB−N-methylpyrrolidine by catalytic hydrogenation using PtO2 in glacial acetic acid. Quantitative 1H NMR integration of PIB initiated from the difunctional aromatic initiator, 5-tert-butyl-1,3-di(2-chloro-2-propyl)benzene, showed exactly two N-methylpyrrole end groups per aromatic initiator residue. Quantitative reaction of PIB chains with N-methylpyrrole could not be obtained with BCl3 systems. In methyl chloride diluent at −45 °C, <10% N-methylpyrrole capping was obtained after 70 min; in 1,2-dichloroethane at −10 °C, 77% of the PIB chains reacted with N-methylpyrrole after 15 min, and no further reaction was observed up to 18 h. In both BCl3 systems, GPC analysis showed the product to be unimodal, indicating the absence of coupling through dialkylation of N-methylpyrrole.

exo-Olefin (methyl vinylidene)-terminated polyisobutylene (PIB) was synthesized in one pot by quenching TiCl4-catalyzed living PIB with a dialkyl (or) diaryl sulfide at −60 to −40 °C, followed by addition of a base (e.g., triethylamine), followed by warming of the reaction mixture to −20 to −10 °C and final termination with methanol. The initiator was 2-chloro-2,4,4-trimethylpentane (TMPCl); the solvent system was 60/40 hexane/methyl chloride, and 2,6-lutidine was used as a nucleophilic additive during polymerization. 1H NMR spectroscopy was used characterize end-group composition of the product PIBs. Increasing yield of exo-olefin end groups was observed in the approximate order of increasing bulkiness of the substituent on the sulfide, i.e., tert-butyl (100%) > isopropyl (98%) > phenyl (70%) > n-alkyl (39–55%). With diisopropyl sulfide (DIPS), optimized yield of exo-olefin (98%) required stoichiometric excess of DIPS relative to chain ends (CE), e.g., [DIPS]/[CE] = 4, addition of a base, and warming of the reaction prior to addition of methanol. With di-tert-butyl sulfide (DtBS), optimized yield was obtained with lesser stoichiometric excess, e.g., [DtBS]/[CE] = 1.5, with or without addition of a base, and with or without warming of the reaction prior to methanol termination. DtBS yielded 100% exo-olefin end groups under concentrated conditions, e.g., [CE] = 0.1 M, and 98% exo-olefin when the reaction was up-scaled to produce 0.8 kg of PIB. The method was successfully adapted to the synthesis of telechelic (difunctional) exo-olefin terminated PIB with quantitative functionality (100%).