Chain transfer reaction to diethylzinc in ethylene polymerization by metallocene catalysts

Abstract

The addition of diethyl zinc into the metallocene catalytic system for ethylene polymerization efficiently reduces the molecular weight of the resulted polyethylene due to the transfer reaction of the propagation chain to the dialkyl zinc. The alkyl exchanging reaction between diethyl zinc and the methylaluminoxane or trimethyl aluminum may result in the new zinc compounds. Therefore, the result of regression analysis shows that the chain transfer is not an ideal first order reaction. The regression result also shows that the transfer reaction to zinc is much stronger than other transfer reaction. The reaction results in the long alkyl zinc, and the latter is easily be oxidized, and then forms the polyethylene contains an abundance of hydroxyl capped chain end, which has been identified by means of 13C-NMR.