Ethylene slurry polymerizations were performed using supported nickel diimine catalysts. The effects of catalyst structure and polymerization conditions on catalyst activity, polymer particle morphology, and polymer properties were investigated. Covalently attached supported nickel diimine catalysts activated with ethyl aluminum sesquichloride (EASC) have high activities and made polymers with spherical morphology. Compared with the equivalent homogeneous catalysts, the covalently attached supported catalysts produced polyethylene with higher melting temperatures, higher molecular weights, and broader molecular weight distributions. Borates used as internal activator during the synthesis of these supported catalysts successfully activated the nickel diimine complexes.
This manuscript shows how two single‐site catalysts can be used to produce polyolefins with complex microstructures that cannot be made using conventional Ziegler‐Natta or Phillips catalysts. In the first case study, thermoplastic polyolefins with heterogeneously branched structures are made by the copolymerization of ethylene, an α‐olefin, and an α‐ω diene using two metallocene catalysts in a two‐stage solution polymerization process. In the second, metallocenes and late transition metal catalysts are co‐supported on silica particles to produce ethylene/α‐olefin copolymers with inverse comonomer distribution in a single slurry reactor, by manipulating the comonomer reactivity ratios and chain walking frequencies of the catalyst pair.
PE/MMT nanocomposites were prepared through in situ polymerization using a nickel diimine catalyst supported on commercially available MMTs such as Cloisite Na+, Cloisite 30B, and Cloisite 93A. XRD patterns revealed that the layers of Cloisite 30B and Cloisite 93A were intercalated after treatment with TMA and the nickel diimine complex. The catalyst supported on Cloisite 30B showed high yields without additional activator and produced nanocomposites with high melting and decomposition temperatures. The thermal properties and crystallinity could be controlled by varying the clay content in the nanocomposite. The morphologies of the resulting particles and the dispersion of the MMT layers in the polymer matrix were characterized by SEM and TEM.magnified image
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