Investigation of the TiCl₄ Reaction Order in Living Isobutylene Polymerizations

Abstract

The reaction order with respect to TiCl4 was investigated in the living polymerization of isobutylene (IB) initiated by 2-chloro-2,4,4-trimethylpentane (TMPCl)/TiCl4 in hexane/methyl chloride (Hx/MeCl) 60/40 v/v cosolvents at −80 °C. It was found that the reaction is more complex than previously believed. The TiCl4 order was found to be closer to 1 at [TMPCl]0 > [TiCl4]0, and closer to 2 when [TMPCl]0 < [TiCl4]0. Kinetic complexity is demonstrated by the fraction order in TiCl4, and the rate-acceleration found when [TMPCl]0 ≫ [TiCl4]0. A comprehensive mechanistic scheme to explain the kinetic behavior of living IB polymerizations is proposed. Further, a new fiber optic mid-IR monitoring method for more convenient kinetic investigations is demonstrated.