Boletín de la Sociedad Chilena de Química
versión impresa ISSN 0366-1644
GUEVARA, JUAN LUIS; ROJAS G., RENE; NARVAEZ, ANA y QUIJADA, RAUL. ESTUDIO DEL COMPORTAMIENTO CATALITICO DE LA HOMO Y COPOLIMERIZACION DE 1-OCTADECENO CON CATALIZADORES METALOCENOS RACEMICOS rac-Et(Ind)2ZrCl2 Y rac-Me2Si(Ind)2ZrCl2. Bol. Soc. Chil. Quím. [online]. 1999, vol.44, n.4, pp. 497-504. ISSN 0366-1644. http://dx.doi.org/10.4067/S0366-16441999000400014.
Catalytic racemic metallocenes of othe type rac-X(Ind)2ZrCl2 (where X = union among indenyl rings, of the type -CH2-CH2-, (CH3)2Si- and (CH3)2C-, and Ind = indenyl) have shown a high catalytic activity for the polymerization of ethylene, propylene and other a-olefins. This paper reports the experimental results of the homopolymerization of a long chain a-olefin such as 1-octadecene (C18) and the copolymerization of ethylene (C2) with that monomer, using two recemic metallocene catalysts: rac-Et(Ind)2ZrCl2 and rac-Me2Si(Ind)2ZrCl2 , which differ in the type of bridge between the indenyl rings (-CH2-CH2-, (CH3)2Si-). 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)2ZrCl2 catalyst incorporates more C18 in the polymer chain than its homologue with an ethyl bridge. These differences are attributed to the type of interannular bond 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°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
Palabras llave : Homopolymerization; copolymerization; metallocene; catalytic activity; poly-1-octadecene.