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Summary The 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.

The controlled cationic polymerization of styrene using CumOH/AlCl 3 OBu 2 /Py initiating system in a mixture CH 2 Cl 2 /n-hexane 60/40 v/v at À40 and À60 C is reported. The number-average molecular weights of the obtained polystyrenes increased with increasing monomer conversion (up to M n ¼ 85,000 g mol À1 ) although experimental values of M n were higher than the theoretical ones at the beginning of the reaction that was ascribed to slow exchange between reversible-terminated and propagating species. The molecular weight distribution became narrower through the reaction and leveled of at the value of M w /M n ¼ 1.8-2.0. A kinetic investigation revealed that the rate of polymerization was first-order in AlCl 3 OBu 2 concentration meaning that monomeric counteranion (AlCl 3 OH À or AlCl À 4 ) involved in the initiation and propagation steps of the reaction. It was also found that the rate of polymerization decreased with lowering temperature, which could be attributed to a decrease in concentration of free Lewis acid (AlCl 3 ), the true coinitiator of polymerization, because of an increase in the tightness of its complex with dibutyl ether.

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