Study of the catalytic behavior of the homo- and copolymerization of 1-octadecene with the racemic metallocene catalysts rac-et(ind)(2)zrcl2 and rac-me2si(ind)(2)zrcl2.

Abstract

Catalytic racemic metallocenes of othe type rac-X(Ind)(2)ZrCl2 (where X = union among indenyl rings, of the type -CH2-CH2-, (CH3)(2)Si- and (CH3)(2)C-, and Ind = indenyl) have shown a high catalytic activity for the polymerization of ethylene, propylene and other alpha-olefins. This paper reports the experimental results of the homopolymerization of a long chain alpha-olefin such as 1-octadecene (C-18) and the copolymerization of ethylene (C-2) with that monomer, using two recemic metallocene catalysts: rac-Et(Ind)(2)ZrCl2 and rac-Me2Si(Ind)(2)ZrCl2, which differ in the type of bridge between the indenyl rings (-CH2CH2-, (CH3)(2)Si-). In the homopolymerization of 1-octadecene there are important differences in the catalytic behavior (activity) between both metallocenes, but not so in the homopolymerization of Ethylene. In the Copolymerization, the difference between the activities of the catalysts increases as the 1-octadecene concentration increases in the reaction medium. Also, the rac-Me2Si(Ind)(2)ZrCl2 catalyst incorporates more C-18 in the polymer chain than its homologue with an ethyl bridge. These differences are attributed to the type of interannular band in the catalysts. The polymers obtained were subjected to thermal analysis using differential scanning calorimetry (DSC). The results show that the poly-1-octadecene synthesized with the catalysts studied have the same type of melting curve, which shows two endotherms at 30 and 54 degrees C. In the copolymers, the increase in the amount of comonomer in the polymer chain leads to a decrease in the melting temperature and in the crystallinity.