Polymerization of Isobutylene by AlCl3/Ether Complexes in Nonpolar Solvent

Abstract

The carbocationic polymerization of isobutylene (IB), co-initiated by AlCl3/ether complexes, has been reexamined and extended to different dialkyl ethers. In the absence of a proton trap, 2,6-di-tert-butylpyridine (DTBP), the polymerization of IB by the cumyl alcohol (CumOH)/AlCl3·nBu2O initiator/co-initiator system in dichloromethane/hexanes (80/20 v/v) at −40 °C gave high conversion to polyisobutylene (PIB) comprising exo-olefins with high selectivity, similar to that reported before by Vasilenko et al.(1, 2) However, in the presence of DTBP, polymerization was absent, suggesting that CumOH is not an initiator in conjunction with AlCl3·Bu2O, and the true initiator is adventitious water. Similarly, in the presence of DTBP in hexanes at 0 °C, polymerizations were absent not only with CumOH but with CumCl, tert-butanol, and 2-chloro-2,4,4-trimethylpentane. The polymerization of IB could be initiated only with adventitious water in the absence of DTBP, but monomer conversions and exo-olefin content (60–70%)...