Tailoring the AlCl(3)/iPr(2)O/Et(2)O initiation system for highly reactive polyisobutylene synthesis in pure n-hexane

This paper reports the flow synthesis of highly reactive polyisobutylenes (HRPIBs) in pure n-hexane using properly prepared AlCl(3)·Et(2)O crystals in conjunction with AlCl(3)·iPr(2)O solution as coinitiators. By preparing AlCl(3)·iPr(2)O solution and AlCl(3)·Et(2)O crystals separately, the cationic polymerization of isobutylene proceeded smoothly under a wide range of monomer concentrations (0.33–1.30 M) in the presence of H(2)O as an initiator, affording a high yield (∼89%) and a moderate exo-olefin terminal group content (60–75%) in 10 min. The various functions of iPr(2)O and Et(2)O in the initiator solution were comprehensively revealed from the polymerization results, attenuated total reflection-Fourier transform infrared and (27)Al nuclear magnetic resonance spectra, and density functional theory simulations. AlCl(3)·iPr(2)O was confirmed to be the key component that stabilized carbenium ions. The AlCl(3)·Et(2)O complex was the key component to promote proton elimination. Free Et(2)O should be removed to inhibit its negative effect on isomerization. This new strategy may lead to high commercial interest in HRPIB synthesis in pure green solvent and could potentially be extended to other initiation systems containing solid Lewis acids.