Abstract
Summary: Branched polyethylene/linear polyethylene blends (BPE/LPE) were prepared using the combined Ni(α‐diimine)Cl~2~ (1) (α‐diimine = 1,4‐bis(2,6‐diisopropylphenyl)acenaphthenediimine) and {Tp^Ms*^}TiCl~3~ (2) (Tp^Ms*^ = hydridobis(3‐mesitylpyrazol‐1‐yl)(5‐mesitylpyrazol‐1‐yl)) catalysts supported in situ on methylaluminoxane (MAO)‐modified silica (4.0 wt.‐% Al/SiO~2~). The polymerization reactions were performed in toluene at two different polymerization temperatures (0 and 30 °C) and several nickel molar fractions (x~Ni~), using MAO as external cocatalyst. At all temperatures, the activities show an approximate linear correlation with x~Ni~, indicating a non‐synergistic effect between the nickel and the titanium species. Higher activities were found at 0 °C. The melting temperatures for the polyethylene blends produced at 0 °C decrease as x~Ni~ increases in the medium, indicating good compatibility between the polyethylene phases made by both catalysts. The melting temperature (T~m~) of the polyethylene blends was shown to depend on the order in which the catalysts were immobilized on the MAO‐modified silica support. The initial immobilization of 1 on the support (2/1/SMAO‐4) affords polymers with a lower T~m~ than those produced with 1/2/SMAO‐4. In addition, scanning electron microscopy (SEM) studies revealed that the spherical morphology of the supported catalyst is replicated in the polyethylene particles.
Influence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying x~Ni~.
magnified imageInfluence of polymerization temperature on the activity of 1/2/SMAO‐4 with varying x~Ni~.