Nobuhide Ishihara

Syndiospecific polymerization of styrene

Syndiotactic polystyrene, namely XAREC® is being developed by Idemitsu Petrochemical Co., Ltd. as a major new polymer family. XAREC® is a new crystalline engineering thermoplastic with a crystalline melting point of 270 °C. Because of its crystalline nature, XAREC® has a high heat resistance, an excellent chemical resistance and a water/steam resistance. XAREC® also has the dip soldering resistance. Potential applications for XAREC® include surface-mount electronic devices and electrical connectors. In this paper, some mechanistic models for polymerization and stereo-regulation as well as the factors which affect the activity and stereospecificity of the catalysts are discussed. The effects of substitutions on Cp ligand of half titanocene complexes were examined. The bulky substitution groups reduce the activity. Also, borate compounds as activator and effects of hydrogen are discussed.

Novel catalysts for syndiospecific polymerization of styrene

The current development of the metallocene-based catalysts for syndiotactic polystyrene (SPS) has been reviewed. SPS is a new semi-crystalline engineering thermoplastic with a crystalline melting point of 270°C. Because of its crystalline nature, SPS has high heat resistance, excellent chemical resistance and waterysteam resistance. In this review, some mechanistic models for polymerization and stereoregulation, as well as the factors which affect the activity and stereospecificity of the catalysts, are discussed.

Recent development of catalysts for syndiospecific polymerization of styrene

Abstract Catalysts for syndiospecific polymerization of styrene are examined. Among the transition metal complexes, complexes with titanium and one cyclopentadienyl(Cp) ligand show high catalyst activity. Titanium complexes with different substituent groups on Cp ligand were examined and a good relationship between electron density of titanium and the space for styrene coordination was found. The bulky substituent groups reduce the catalyst activity and electron donative substitution groups increase the catalyst activity. Small amount of hydrogen increases the catalyst activity. However, excess amount of hydrogen makes molecular weight distribution broaden. There seems to be two kinds of active site for the styrene polymerization under the conditions. Titanium complexes with various types of tetraphenylborates were examined. The number of fluorine on the phenyl group of borate improves the catalyst activity and by-products from the reaction of triisobutylaluminum, borate and titanium complex may coordinate the active site and decrease the catalyst activity.