Polish version

Login form

register


Print

K. Niciński, D. Jamanek, W. Skupiński, M. Borowiak

Influence of hydrogen and methane on the polymerization of styrene in the presence of CpTiCl2(OC6H4Cl-p)/MAO catalytic system (in English)

Polimery 2007, No 6, 421


Summary

The effect of hydrogen or methane on the course of styrene syndiotactic polymerization in the presence of CpTiCl2(OC6H4Cl-p)/MAO catalytic system (Cp - cyclopentadienyl, MAO - methylalumoxane) was investigated. The effects of contact time and pressure on the yield, weight - average molecular weight (Mw) and molecular weight distribution MWD as well as on the syndiotacticity index of the polymers obtained were determined. It was found that prolonged contact time of methane with reaction mixture caused significant decrease in yield and slight decrease in polymer molecular weight with simultaneous increase in PS syndiotacticity index. The effect of increasing pressure of methane is similar. However, prolonged contact time and increasing pressure of hydrogen caused increasing yield and clear decrease in molecular weight of the product. The change in the mechanism of initiation of stereospecific styrene polymerization, caused by methane, was interpreted on the basis of EPR spectra analyses. The formation of monohydrogen complexes of titanium as a result of reaction with methane or catalytic system itself, or dimeric Ti complexes formed in the stage of polymer chain termination has been found.


Key words: stereospecific styrene polymerizaton, hemititanocene catalysts, hydrogen or methane presence, initiation mechanism, EPR investigations


e-mail: k.nicinski@ipgum.pl


K. Niciński, D. Jamanek, W. Skupiński, M. Borowiak

Influence of hydrogen and methane on the polymerization of styrene in the presence of CpTiCl2(OC6H4Cl-p)/MAO catalytic system (in English)