Copolymerization and characterization of ethene-1-hexene copolymers prepared by using the (Me5Cp)(2)ZrCl2-MAO catalyst system

It is demonstrated that the catalyst system bis(pentamethylcyclopentadienyl )-zirconium dichloride (Me5Cp)(2)ZrCl2-methylaluminoxane (MAO) is able to p roduce random copolymers of ethene and l-hexene. The l-hexene incorporation in the copolymers is extremely small. Even in the case of a molar ratio of [ethene] to [1-hexene] of 1/20 in the monomer feed, only 1.4 mol % 1-hexen e are incorporated according to C-13 nuclear magnetic resonance (NMR) spect ra. Nevertheless, the physical properties of the random copolymers change s ignificantly in this small range of l-hexene incorporation, from a high-den sity polyethene to a linear low-density polyethene. Thus, the melting tempe rature, the degree of crystallinity, the density and lamella thickness, and the long period of the alternating crystalline and amorphous regions decre ase with increasing I-hexene content in the random copolymers. Blends of hi gh-density polyethene prepared with the system (Me5Cp)(2)ZrCl2-MAO and an e lastomeric random copolymer of ethene and l-hexene are phase-separated and show good compatibility, as demonstrated by transmission electron microscop y. (C) 1999 John Wiley & Sons, Inc.It is demonstrated that the catalyst sys tem bis(pentamethylcyclopentadienyl)-zirconium dichloride (Me5Cp)(2)ZrCl2-m ethylaluminoxane (MAO) is able to produce random copolymers of ethene and l -hexene. The l-hexene incorporation in the copolymers is extremely small. E ven in the case of a molar ratio of [ethene] to [1-hexene] of 1/20 in the m onomer feed, only 1.4 mol % l-hexene are incorporated according to C-13 nuc lear magnetic resonance (NMR) spectra. Nevertheless, the physical propertie s of the random copolymers change significantly in this small range of l-he xene incorporation, from a high-density polyethene to a linear low-density polyethene. Thus, the melting temperature, the degree of crystallinity, the density and lamella thickness, and the long period of the alternating crys talline and amorphous regions decrease with increasing I-hexene content in the random copolymers. Blends of high-density polyethene prepared with the system (Me5Cp)(2)ZrCl2-MAO and an elastomeric random copolymer of ethene an d l-hexene are phase-separated and show good compatibility, as demonstrated by transmission electron microscopy. (C) 1999 John Wiley & Sons, Inc.