Cationic olefin polymerization using alkyl halide alkylaluminium initiator systems

Abstract

The effect of t-BuX, Et₂AlX and EtAlCl₂, MeX and temperature on PIB molecular weight has been studied by GPC and viscometry. A large amount of $\overline M _{\text{n}} , \overline M _{\text{w}}$, MWD as well as $\overline M _{\text{v}}$ and $\Delta E_{\overline {\text{M}} _{\text{v}} }$ (activation energy of viscosity average molecular weight) data were generated. Influence of monomer concentration on $\overline M _{\text{n}}$ and $\overline M _{\text{v}}$ was analyzed by Mayo plots and relative rate constants were calculated. Predominant molecular weight controlling mechanisms in t-BuCl and t-BuBr/Et₂AlCl/MeCl systems were determined.

A relation between $\Delta E_{\overline {\text{M}} _{\text{v}} }$ and molecular weight controlling mechanisms was discovered and the effect of initiator system, solvent and temperature on $\Delta E_{\overline {\text{M}} _{\text{v}} }$ was explained. The present work has led to an understanding of the effect of counteranion on PIB molecular weight. These studies provide better insight into the detailed mechanism of isobutylene polymerization, in particular into the initiation and the molecular weight controlling events.