SYNTHESIS AND PROPERTIES OF HOMOPOLYMER AND COPOLYMERS OBTAINED FROM 1-OCTADECENE WITH ZIRCONOCENE CATALYSTS

 Studies related to the behavior of different metallocene catalysts for the homopolymerization of 1-octadecene andits copolymerization with ethylene will be presented. The metallocenes: rac-Et(Ind)₂ZrCl₂, rac-Me₂Si(Ind)₂ZrCl₂ andPh₂C(Flu)(Cp)ZrCl₂ were chosen for the homopolymerization study. They show important differences in catalytic activity athigh temperatures (≥70℃), with rac-Et(Ind)₂ZrCl₂ showing the highest activity. At lower temperatures (≤30℃) thedifferences are negligible. For the copolymerization of ethylene with 1-octadecene only the catalysts rac-Et(Ind)₂ZrCl₂ and rac-Me₂Si(Ind)₂ZrCl₂ were studied.The results show that their catalytic activity is just like that for the homopolymerization of 1-octadecene,with higher activity for the metallocene with the Et-bridged catalyst.¹³C-NMR analysis shows that the composition of the copolymerization products depends on the catalytic systems.Copolymers obtained with rac-Me₂Si(Ind)₂ZrCl₂ have greater comonomer incorporation.Thermal analysis shows that poly-1-octadecene synthesized with the catalyst rac-Et(Ind)₂ZrCl₂ is very dependent on the polymerization temperature.The homopolymer obtained at 70 ℃ presents two endothermal peaks at 41℃ and 53℃,as compared with the one obtained at 30℃ which presents one wider peak with a maximum at 67℃.For the catalyst rac-Me₂Si(Ind)₂ZrCl₂ this trend is not observed.The type of metallocene and the reaction time do not significantly change the intrinsic viscosity,but the polymerization temperature changes it drastically,giving higher values at lower temperature.Viscosity measurements on the copolymers show that an increase of comonomer concentration in the feed reduces the molecular weight of the copolymer,and it was also found that for homopolymer,the molecular weight is independent of the catalytic systems.