Ethylene polymerization with hybrid nickel diimine/Cp2TiCl2 catalyst: a new method to prepare blends of linear and branched polyethylene

Abstract

AbstractBlends of linear polyethylene (LPE) and branched polyethylene (BPE) display very good mechanic properties that can be beneficial for various applications such as shear thinning and melt elasticity. LPE, BPE and amorphous polyethylene can be produced using nickel diimine (DMN) catalyst under various polymerization conditions, while LPE can be obtained using metallocene catalyst. Thus, LPE/BPE blends can be achieved by in situ polymerization using a hybrid DMN/metallocene catalyst. A novel hybrid catalyst made of DMN and Cp2TiCl2 was designed and used for ethylene polymerization. A synergistic effect of the two active sites in the hybrid DMN/metallocene catalyst was observed. Blends of linear and low branched polyethylene were synthesized when polymerization was conducted at low temperature (0 °C), while blends of linear and highly branched polyethylene were obtained at high temperature (50 °C). However, the miscibility of the polymers obtained at 50 °C was dramatically reduced as compared to those obtained at 0 °C. Mesoporous particles (MCM‐41) consisting of aluminosilicate with cylindrical pores were used to support the hybrid catalyst, in which MCM‐41 provides sufficient nanoscale pores to facilitate the polymerization in well‐controlled confined spaces. Blends of LPE and BPE were synthesized by in situ polymerization without adding comonomer and characterized. The miscibility of the polymer blends can be improved by supporting the hybrid catalyst on MCM‐41. Copyright © 2009 Society of Chemical Industry