Synthesis and properties of ethylene/styrene copolymers produced by metallocene catalysts

Ethylene/styrene copolymers were synthesized under constant polymerization conditions using six different metallocene catalysts activated with methylaluminoxane. For all the catalysts used, the activity and molecular weight of the copolymers produced decreased with the amount of styrene in the reactor feed, but the styrene content of the copolymers increased. Catalysts with carbon bridges and bulky ligands gave rise to copolymers with higher styrene content. As a result of the increased styrene content of the copolymer, the melting temperature decreased. This effect was ascribed to a decrease in the crystallinity of the copolymers. It was also found that lamellar thickness could be significantly diminished by the incorporation of comonomers. The copolymers showed a broad spectrum of mechanical properties as a function of the comonomer ratio. At low styrene contents, they behaved like typical semicrystalline thermoplastics, and at higher styrene contents, they exhibited the properties typical of elastomers. Of the catalysts tested, [rac-ethylenebis(4,5,6,7-tetrahydro-1-indenyl)]zirconium dichloride emerged as the most promising for the production of ethylene/styrene copolymers. (c) 2006 Wiley Periodicals, Inc.