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

摘要

The cationic polymerization of isobutylene using AlCl3xOBu2 and AlCl3xO~iPr2 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 (Mn1/41,500-2,500 g mol~(-1)) and high exo-olefin content (85-90%) were synthesized at high monomer concentration ([M]1/45.2-7.8M) and high reaction temperature (0 °C-20 °C) with both of catalytic complexes. In n-hexane, AlCl3xOiPr2 showed considerably higher activity and selectivity towards b-H abstraction that AlCl3x 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 (Mn1/43,500- 10,000 g mol~(-1)) than required for the commercial application.