A cost-effective process for highly reactive polyisobutylenes via cationic polymerization coinitiated by AlCl3

The initiating system consisting of AlCl3 with dialkyl ether such as di-n-butyl ether or diisopropyl ether has been successfully developed for providing a cost-effective process of synthesis of highly reactive polyisobutylenes (HRPIBs) with large proportion of exo-olefin end groups up to 93 mol% at temperatures ranging from −20 to +20 °C. The above dialkyl ethers played very important roles in promoting the directly rapid β-proton elimination from –CH3 of the growing chain ends to create exo-olefin end groups and decreasing or even suppressing the carbenium ion rearrangements to form the double bond isomers. Very importantly, the highly reactive PIBs with 80–92 mol% of exo-olefin end groups, having low Mns of 1300–2300 g mol−1 and monomodal molecular weight distribution (Mw/Mn = 1.7–2.0) could be achieved at 0–20 °C. These results are comparable to those of commercial HRPIBs produced industrially by the best BF3-based initiating system at far below 0 °C.