Structure and Properties of Poly-α-olefins Containing Quaternary Carbon Centers

In this paper, poly-α-olefins (PAO) containing quaternary carbon centers were prepared by two-step oligomerization using a metallocene catalyst followed by a Ziegler-Natta catalyst. First, the 1-decene dimer was oligomerized with [t-BuN(Me)₂C(η⁵-C₅H₄)]ZrCl₂, and the effects of the oligomerization temperature, Al/Zr molar ratio, and catalyst loading on the oligomerization were investigated. In the second step, the obtained 1-decene dimers were copolymerized with 1-decene with TiCl₄/Et₂AlCl, and the effects of the catalysts, monomer/dimer ratio, and α-olefin species on the copolymerization were investigated. The composition and structure of the dimers and copolymerization products were characterized by gas chromatography (GC) and ¹H NMR and ¹³C NMR spectroscopy. The results of GC and ¹³C NMR analyses indicated that the metallocene catalyzed the formation of the 1-decene oligomerization product, resulting in the branched olefin dimer being the major product, and the existence of quaternary carbons in the 1-decene/1-decene dimer copolymerization product could also be found. The polymerization mechanism for the formation of the quaternary carbon centers is proposed. The 1-decene/1-decene dimer copolymerization product containing quaternary carbon centers has a kinematic viscosity of 10.8 mm²/s at 100 °C, a viscosity index of 165, and a pour point of -52 °C; thus, the product with quaternary carbon centers has a better viscosity-temperature performance and low-temperature fluidity than those of the 1-decene oligomerization product and typical PAO products, but the kinematic viscosity is similar.