Synthesis and characterization of copolymers of ethylene and 1-octadecene using the rac-Et(Ind)2ZrCl2/MAO catalyst system

Abstract

SUMMARY: The copolymerization of ethylene and 1-octadecene using a bridged metallocene was studied in order to observe the effect of the comonomer on the catalytic activity. A noticeable increase in activity is seen as the concentration of 1-octadecene in the reaction medium increases. 13C NMR analysis shows 6.4 mol-% incorporation of comonomer at the highest 1-octadecene concentration in the feed used here. The molecular weight of the copolymers shows a drastic decrease that may be attributed to chain termination by transfer or b-elimination of the comonomer. As to the molecular weight distribution, it remains within a narrow range, as expected with metallocene catalysts. The melting temperature and the enthalpy of melting of the copolymers show a decrease with increasing comonomer content. As usual for ethylene copolymers, the X-ray crystallinities are higher than those determined from the enthalpy of melting.

Combined polymerization catalysis of nickel complex and zirconocene for branched polyethylene

“…The polymer produced by method I has the lowest melting point (Entry 2, T m = 112.67ºC, ® c = 38.5) compared to the polymer produced by method III which has the highest melting point (Entry 3, T m = 130.79ºC, ® c = 55.2). The lower melting point of polyole¯n often means the higher branching value [4,16]. In method I, more oligomers were produced due to the addition of the nickel catalyst at¯rst, consequently more oligomers were copolymerized to form polyethylene with more branches.…”

“…The reaction temperature has also been adapted in order to examine the e®ects on the activity and the copolymerization behavior of the catalyst [4]. In Entries 13, 14, 2 and 15 (in Table 3), the reaction temperatures were ranged from -10ºC to 50ºC.…”

“…Consequently many e®orts have been made to design novel and convenient catalytic systems for such polyole¯ns [2,3,4,5,6]. So far there are two ways to get the LLDPE: one is the copolymerization of ethylene and ®-ole¯ns by Ziegler-Natta catalyst or metallocene catalyst, the other is a catalytic system capable of simultaneously oligomerizing and copolymerizing sole ethylene.…”

A Study on the Coordination Polymerization Using C2-Symmetric Dichloro[rac-ethylenebisindenyl] zirconium(IV)/Methylaluminoxane System

“…This was attributed to the "positive" comonomer (1-decene) effect: (1) enhanced solubility of the copolymer (PED) in comparison with that of the homopolymer (PE), which favored monomer diffusion to the active center; (2) comonomer activation of new catalyst sites by increased affinity for the metallocene catalyst; (3) increased solubility of the monomer in the liquid phase due to the presence of the comonomer, which increased its insertion rate. 17 In the case of the terpolymer, the catalytic activity is lower than that of the copolymer (PED). This may have been due to the "negative comonomer (p-MS) effect."…”

Study of the Effect of Branching in Degradation of Polyethylenes Obtained via Metallocene Catalyst

“…The advent of metallocene catalysts has made possible the production of various tailor-made polymers [1][2][3][4] to satisfy industrial and end user requirements. This is due to the fact that metallocene catalysts are single-site catalysts that lead to narrower molecular weight distribution and more uniform structure than traditional Ziegler-Natta catalysts.…”