| Abstract
| - The titanium catalyst (C5(CH3)4Si(CH3)2NR)TiCl2 has been tethered to the interior pore surfaces ofp-aminophenylsilyl-functionalized mesoporous silica materials in a single-step process to form supportedconstrained-geometry catalysts (CGCs), and the polymerization of ethylene and copolymerization ofethylene and 1-octene by the resulting heterogenized CGCs have been studied. Confirmation that theintended supported CGC is correctly assembled and is the only catalytically active species is providedby spectroscopic characterization (29Si CP MAS NMR) and by ethylene/1-octene copolymerization. Theuse of tailored mesoporous silica supports with different uniform pore sizes (25−70 Å) permits investigationof the influence of the structure of the support matrix (i.e., the “second sphere of influence”, where theligand environment provides the primary influence) on catalyst activity and on product properties.Homopolymerization of ethylene by the supported CGCs shows a clear trend in the crystallinity of thehigh-density polyethylene (HDPE) produced, with a higher degree of crystallinity observed for HDPEformed by the heterogenized CGC within the smaller-pore substrates. The observation that a “secondsphere of influence” is indeed significant introduces an additional tunable parameter for the tailoredsynthesis of polyolefins using supported catalysts.
- A titanium catalyst tethered to the interior pore surfaces of mesoporous silica of different uniform pore sizes (25−70 Å) is used to probe the “second sphere of influence” of the substrate on catalyst activity and product properties. Polyethylene with a higher degree of crystallinity is formed within smaller-pore substrates.
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