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

The influence of the type of solvent on styrene polymerization behavior wit h cyclopentadienyltitanium trichloride (CpTiCl3) and methylalumoxane (MAO) catalytic system at 25 degreesC was investigated. It was found that the num ber-average molecular weight ((M) over bar (n)) of the polystyrene produced was correlated with the dielectric constant of solvent (epsilon). The maxi mum (M) over bar (n) was obtained by using the solvents having proper diele ctric constant at epsilon = 4.0-4.2. The kinetic analyses and H-1 NMR measu rements strongly suggested that this solvent effect was induced by the decr ease of rate constant of beta -hydride elimination (k(tr)(beta)). The corre lation between the kinetic parameters and the dielectric constants of solve nt suggests competitive equilibrium between coordination of solvent and bet a -agostic interaction should exist.