Thomas H. Newman

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.

The influence of phenylsilane on the syndiotactic polymerization of styrene with η5‐pentamethylcyclopentadienyl titanium trifluoride

The syndiotactic polystyrene polymerization activity of a fluorinated half-sandwich complex, η 6 -pentamethylcyclopentadienyl titanium trifluoride (Cp * TiF 3 ), in the presence of relatively low amounts of methylalumoxane (MAO; MAO/Cp * TiF 3 molar ratio = 200/1) and triisobutylaluminum, is significantly increased by the addition of phenylsilane in molar ratios to Cp * TiF 3 ranging from about 300/1 to 600/1, if the phenylsilane is added to the monomer. Lower amounts of phenylsilane, such as a 100/1 molar ratio to Cp * TiF 3 , lead to a reduced polymerization activity in comparison with styrene without phenylsilane. A prereaction of phenylsilane with the catalyst mixture shows a behavior that is strongly dependent on the storage time of the composition and the temperature. A storage time of about 16 h is sufficient to reduce the polymerization conversion to about half of the original value. The results are discussed on the basis of a chain-transfer reaction with phenylsilane and several catalyst complexes of different stabilities and activities, including an alkylation product of phenylsilane.

Effect of phenylsilane on the syndiospecific polymerization of styrene in the presence of half-sandwich metallocenes

Abstract The syndiotactic polymerization of styrene with two selected half-sandwich metallocenes, η5-pentamethylcyclopentadienyl titanium trichloride and η5-octahydrofluorenyl titanium trimethoxide, has been investigated in the presence of phenylsilane. In dependence of the addition of this component, it shows a different effect on the styrene polymerization. Added to the monomer, the phenylsilane significantly accelerates the polymerization and reduces the molecular weight of the syndiotactic polystyrene acting as a chain-transfer agent for both catalysts. At reasonable reaction times of phenylsilane with the premix containing the metallocene, methylalumoxane and triisobutylaluminum, it reduces the polymerization conversion below the level of the polymerization without phenylsilane. Whereas the molecular weights and the polydispersities of the polymers are about the same with increasing phenylsilane concentration in the case of the η5-pentamethylcyclopentadienyl titanium trichloride, both properties are increasing with η5-octahydrofluorenyl titanium trimethoxide as a catalyst, indicating a difference in the active sites of polymerization. Possible reasons for this reaction behavior are discussed on the basis of polymerization results, molecular weight distributions, thermal properties of the syndiotactic polystyrenes, and EPR measurements with both catalysts.