Primary Halide-Terminated Polyisobutylene: End-Quenching of Quasiliving Carbocationic Polymerization with N-(ω-Haloalkyl)pyrrole

N -(ω-Haloalkyl)pyrroles (1-(2-chloroethyl)pyrrole, 1-(2-bromoethyl)pyrrole, and 1-(3-bromopropyl)pyrrole) were used to end-quench quasiliving isobutylene (IB) polymerizations initiated from 2-chloro-2,2,4-trimethylpentane (TMPCl)/TiCl 4 or 5- tert -butyl-1,3-di(2-chloro-2-propyl)benzene ( t -Bu- m -DCC)/TiCl 4 at −70 °C in hexane/CH 3 Cl (60/40, v/v). Prechilled N -(ω-haloalkyl)pyrrole, either neat or in a solution of the reaction solvents, was charged to the polymerizations at full (>98%) IB conversion. In all cases, quantitative end-capping of about 0.03 M chain ends (CE) was achieved within 4 min using [ N -(ω-haloalkyl)pyrrole] = 2[CE] and [TiCl 4 ] = 1.5[ N -(ω-haloalkyl)pyrrole]. 1 H NMR analysis revealed mixed isomeric end groups in which polyisobutylene (PIB) was substituted at either C 2 or C 3 of the pyrrole ring. The isomer ratio C 2 /C 3 was observed to be effected by the alkylene tether length. N -(2-Haloethyl)pyrroles yielded isomer ratios C 2 /C 3 in the range 0.26/0.74 to 0.29/0.71; 1-(3-bromopropyl)pyrrole yielded C 2 /C 3 in the range 0.38/0.62 to 0.40/0.60. GPC indicated the absence of coupled PIB, confirming exclusive monosubstitution on each pyrrole ring. Complete 1 H and 13 C NMR chemical shift assignments were made for both isomers produced from each of the three quenchers. 1 H NMR integration of PIB initiated from the difunctional aromatic initiator, t -Bu- m -DCC, showed two N -(ω-haloalkyl)pyrrole end groups per aromatic initiator residue.