Investigation of the TiCl4 reaction order in living isobutylene polymerizations

The reaction order with respect to TiCl4 was investigated in the Living pol ymerization of isobutylene (IB) initiated by 2-chloro-2,4,4-trimethylpentan e (TMPCl)/TiCl4 in hexane/methyl chloride (Hx/MeCl) 60/40 v/v cosolvents at -80 degrees C. It was found that the reaction is more complex than previou sly 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. Furt her, a new fiber optic mid-IR monitoring method for more convenient kinetic investigations is demonstrated.