NMR Study of Branched Polyethylenes Obtained with Combined Fe and Zr Catalysts

Abstract

The products obtained with the system {[(ArNC(Me))2C5H3N]FeCl2}/MAO (Ar = 2-C6H4(Et)) (1) and the ones obtained by the use of 1 in conjunction with Me2SiInd2ZrCl2/MAO (2) or EtInd2ZrCl2/MAO (3) were completely characterized by 1H NMR and 13C NMR. Catalyst 1 gives mainly linear α-olefins of molecular weights close to 2000 g/mol and a low amount of alkanes. The use of 1 with 2 or 3 using only ethylene as monomer gives branched polyethylene with ethyl, butyl, and mainly long branches. Some amount of unreacted α-olefin was also found in some cases, especially in reactions where a high ratio Fe to Zr was used.

Tandem catalytic system: Rac‐Et(ind)2ZrCl2/AlEt2Cl/MAO toward the synthesis of branched polyethylene

“…The nomenclature adopted for the polymer backbone and branching carbons is defined by Usami et al, 34 and the branching degree is calculated according to the literature. 7 Analysis of the polymer sample by 13 C NMR shows that the polymer contains degrees of branching, with C 2 , C 4 , and C 6 branches. The density of ethyl branches is 19 per thousand carbons, whereas the densities of butyl and long branches are 6.5 and 0.9 per thousand carbons, respectively.…”

“…5 C and v c of 68.3%, a parallel result was also gained (T m ¼ 130. 7 C and v c ¼ 65.3%, Run 1) at varied pressure reaction condition under rac-Et(Ind) 2 ZrCl 2 /MAO system. These results indicate that the branched polyethylene cannot be prepared though changing the reaction pressure in catalytic system rac-Et(Ind) 2 ZrCl 2 /MAO.…”

“…After that, a wide variety of promising tandem catalytic systems have been developed to prepare LLDPE in situ involving two different Ziegler-Natta catalysts, Ziegler-Natta catalyst/ homogeneous catalyst, two or three different homogeneous catalysts. [3][4][5][6][7][8][9][10] Surveying these works, [11][12][13][14][15][16] it is found that tandem catalysis is consisted of two kinds of catalysts and one activator, in which one catalyst oligomerizes the ethylene to a-olefins, and the other is responsible for polymerizing the ethylene and incorporating the a-olefins into the growing polymer chain under the same activator. In other words, the essential of tandem catalysis exists a dual functional catalyst active species: oligomerization/copolymerization active species in the same reaction system.…”

Combined polymerization catalysis of nickel complex and zirconocene for branched polyethylene

“…For example, the branches of resulting polyethylene was 11.8 when the Ni/Zr molar ratio was 2:7 ( Figure 3), and increased to 14.8 for the Ni/Zr molar ratio of 9:2 ( Figure 4). The 13 C NMR results ( Figures 3 and 4) showed that the branches were mainly ethyl [11], which con¯rmed mainly butylenes formed by the Ni catalyst. According to Table 2, the activity of the Zr catalyst has higher activity in higher Ni/Zr.…”

“…In 1995, Brookhart group found that a single late-transition metal catalytic system could transfer sole ethylene to a high branched polyole¯n [8], and also made a bright in°uence for ethylene oligomerization and polymerization by late-transition metal complexes as catalysts. Recently ethylene polymerization for branched polyethylene by combined catalytic system of two catalysts in-situ is becoming the new interest [6,9,10,11]. The combination of zirconocene and late transition metal catalysts is relied on their same cocatalyst, methylaluminoxane (MAO).…”