Highly Reactive Polyisobutylenes via Cationic Polymerization of Isobutylene by AlCl3/Ether Complexes in Non‐Polar Media: Scope and Limitations

Abstract

SummaryThe cationic polymerization of isobutylene using AlCl3 × OBu2 and AlCl3 × OiPr2 as co‐initiators in two non‐polar solvents (toluene and n‐hexane) at different temperatures and monomer concentrations has been investigated. In toluene, highly reactive polyisobutylene (HR PIB) with desired low molecular weight (Mn = 1,500–2,500 g mol−1) and high exo‐olefin content (85–90%) were synthesized at high monomer concentration ([M] = 5.2–7.8 M) and high reaction temperature (0 °C–20 °C) with both of catalytic complexes. In n‐hexane, AlCl3 × OiPr2 showed considerably higher activity and selectivity towards β‐H abstraction that AlCl3 × OBu2 and allowed to synthesize HR PIB with high functionality (exo ≥ 80%) only at –20 °C, but the molecular weight of synthesized PIB is slightly higher (Mn = 3,500–10,000 g mol−1) than required for the commercial application.