Quasiliving Cationic Polymerization of Isobutylene with FeCl3×iPrOH as Co-Initiator in Toluene: A Step Toward Greener Process

Abstract

A quasiliving carbocationic polymerization of isobutylene (IB) in toluene using DiCumCl/FeCl₃×ⁱPrOH initiating system at −80°C is investigated. The optimal composition of catalytic complex is found to be FeCl₃×1.0ⁱPrOH, while at lower content of ⁱPrOH in a complex side reactions occur resulting in generation of monofunctional polyisobutylene (PIB) fraction. The experiments at different monomer to initiator ratios in conjunction with chain extension experiment confirm the quasiliving nature of the polymerization resulting in well-defined difunctional low molecular weight PIB (M_n from 1200 to 7000 g⋅mol⁻¹, Đ < 1.3). Synthesis of higher molecular weight PIB in toluene leads to the gelation of the polymerization system, hence, the toluene/n-hexane 50:50 v/v mixture is successfully used for the synthesis of PIB with M_n up to 52 000 g⋅mol⁻¹ with low dispersity Đ < 1.3. In addition, one-pot syntheses of end-functional PIB are conducted in toluene resulting in vinylidene- and hydroxyl-terminated PIBs with near quantitative functionality.