Solvent effect on beta-hydride elimination reaction in syndiospecific styrene polymerization with cyclopentadienyltitanium trichloride (CpTiCl3)/methylalumoxane (MAO) catalytic system

摘要

The influence of the type of solvent on styrene polymerization behavior with cyclopentadienyltitanium trichloride (CpTiCl3) and methylalumoxane (MAO) catalytic system at 25 degreesC was investigated. It was found that the number-average molecular weight ((M) over bar (n)) of the polystyrene produced was correlated with the dielectric constant of solvent (epsilon). The maximum (M) over bar (n) was obtained by using the solvents having proper dielectric constant at epsilon = 4.0-4.2. The kinetic analyses and H-1 NMR measurements strongly suggested that this solvent effect was induced by the decrease of rate constant of beta -hydride elimination (k(tr)(beta)). The correlation between the kinetic parameters and the dielectric constants of solvent suggests competitive equilibrium between coordination of solvent and beta -agostic interaction should exist. References: 28