Copolymerization of Ethylene and Vinyl Trimethoxysilane with α-Diimine Nickel (II) Catalysts

A series of α-diimine nickel (Ⅱ) catalysts, in the presence of ethylaluminum sesquichloride (EASC) as cocatalyst, were applied in the copolymerization of ethylene and vinyl trimethoxysilane (VTMoS). The effects of polymerization parameters, including catalyst structure, VTMoS concentration, catalyst dosage, molar ratio of Al/Ni (n_Al/n_Ni), ethylene pressure, reaction time and solvent on the copolymerization were investigated. The optimized catalytic reaction conditions were obtained. High temperature NMR (Nuclear Magnetic Resonance), Fourier infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC) were used to characterize the microstructures and melting points of the copolymers. Inductively coupled plasma (ICP) was applied to determine the silicon content of the copolymers. Equilibrium swelling method was used to study the crosslinking degree of copolymers. The results showed that the catalytic activity of C4 reached 6.53 × 10⁵ g/(mol·h) under the optimal conditions: Catalyst dosage was 5.0 μmol, c(VTMoS) = 0.5 mol/L, n_Al/ n_Ni = 400, p(\rmC_2\rmH_4) =1.0 MPa , T = 25 ℃, t = 0.5 h. The mass fraction of silicon in the copolymer was 2.10%.