Cationic polymerization of isoprene initiated by 2-cyclohexylidene ethanol–B(C6F5)3: an insight into initiation and branching reactions

Abstract

In this paper, the cationic polymerization of isoprene using 2-cyclohexylidene ethanol–B(C₆F₅)₃ as the initiating system is investigated under various polymerization conditions. The use of this allylic alcohol allows studying the initiation as well as the mechanism of branching reactions. Intensive β-H elimination, which is the major termination process, is responsible for protic initiation and double bond loss via protonation. This latter process leads to chain branching and intramolecular cyclization, even at low conversion. Independently of the condition used (solvent polarity, temperature, presence of a proton trap, etc.) only oligomers are obtained, composed of saturated sequences and IP units almost exclusively with a 1,4-trans configuration and an olefinic terminal group.