| Developments in single-site catalysts for olefin polymerization have offered unprecedented freedom in designing new polyolefins, controlling polyolefin structure, and tailoring materials properties. The main theme of this sandwich-style thesis is the synthesis, characterization, and properties of a novel series of polyolefin materials that have unique chain structures and superior materials properties. These polyolefin materials were respectively prepared with a variety of recently developed single-site catalysts.;High-strength polyethylene fibers were in situ synthesized via nano-extrusion polymerization of ethylene with a mesoporous particle (MCM-41) supported titanocene catalyst, Cp2TiCl2. The unique nanotube structure prevented the conventional folding of growing polymer chains inside the nanotubes and thus led to the formation of polyethylene nanofibrils with unique extended chain crystalline structure. Further aggregation of nanofibrils resulted in macro-scaled polyethylene microfibers. The morphological properties of nascent PE fibrous materials were investigated extensively using ESEM, XRD, and DSC. Tensile mechanical analyses showed that the polyethylene microfibers produced in this nanofabrication process exhibited tensile strength comparable to those of polyethylene fibers fabricated through post-reactor processing methods.;A Ni/alpha-diimine catalyst, 1,4-bis(2,6-diisopropylphenyl) acenaphthene diimine nickel(II) dibromide, was supported on various mesoporous particles (MCM-41 and MSF) having different nanotube structures to produce short chain branched polyethylenes by ethylene polymerization. The effects of catalyst supporting methods and nanotube structure of the mesoporous particles on the catalyst impregnation were studied. In ethylene polymerization, some active sites of the supported catalysts showed reduced chain walking ability compared to the homogeneous counterparts. The effects of nanotube structure of mesoporous particles on ethylene polymerization activity, polymer property, and polymer particle morphology were investigated. (Abstract shortened by UMI.)... |
