Polymer-supported half-titanocene catalysts for the syndiospecific polymerization of styrene

Monocyclopendienyltitanium trichloride (CpTiCl3) was supported on polymer c arriers with different hydroxyl contents, and the supported catalysts were used for styrene polymerization. The supported catalysts exhibited high act ivity even at low Al/Ti ratios and increased the molecular weight of the pr oducts, indicating that polymer carriers could stabilize the active sites. The polymers prepared with unsupported and supported catalysts were extract ed with boiling n-butanone and characterized by carbon nuclear magnetic res onance (C-13 NMR) and differential scanning calorimetry. The polymers obtai ned by supported catalysts had a high fraction of boiling n-butanone-insolu ble part and high melting temperatures, but C-13 NMR results showed that sy ndiotacticity decreased compared with that of polymers prepared with an uns upported catalyst. ESR study on the supported catalysts confirmed that the active sites supported on the carrier dropped into the solution and formed active sites the same as those in the unsupported system when they reacted with methylaluminoxane. C-13 NMR analysis showed that the polymerization me chanism of the supported active sites was an active-site controlled mechani sm instead of a chain-end controlled mechanism of the unsupported active si tes. (C) 2000 John Wiley & Sons, Inc.