Effect of co- and non copolymerizable lewis bases in propylene polymerization with EtInd2ZrCl2/MAO

FERREIRA, MARÍA LUJÁN; BELELLI, PATRICIA GABRIELA; DANIEL EDUARDO, DAMIANI

MACROMOLECULAR CHEMISTRY AND PHYSICS

Wiley

Año: 2001 vol. 202 p. 830 - 839

1022-1352

This paper reports the effect of co- and non-copolymerizable Lewis bases in propylene polymerization with the soluble system EtInd2ZrCl2/MAO. With non-copolymerizable Lewis bases, the activity and the molar mass of poly(propylene) are diminished. This result is unusual because there is agreement about the cationic nature of the active site in Zirconocene/MAO systems and the effect of a Lewis base must be to decrease the termination constant versus the propagation constant, considering the diminished electrophilicity of Zr. In the case of copolymerizable Lewis bases, the negative effect on activity is higher. An explanation of the data is given, with a new model of Lewis bases/cationic Zr interaction, taking account of recent reports about the structure of active sites.