• Applied Chemistry
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• v.15 no.2
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• pp.85-88
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• 2011

We synthesized ethylene-styrene copolymer by coordination polymerization using 2 types of pyrazolato metallocene catalysts ((1,2,4-Me₃C₅H₄)TiCl₂(3,5-iPr₂C₃HN₂), (tert-BuC₅H₄) TiCl₂(3,5-iPr₂C₃HN₂)). We observed the effects of styrene concentration on the catalytic activity, yield, molecular weight and molecular weight distribution.

• Korean Chemical Engineering Research
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• v.54 no.4
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• pp.574-581
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• 2016

In this study, CNT functionalized with pyrrolidine ring via 1,3-dipolar cycloaddition reaction with various amino acid and aldehyde was synthesized. Metallocene was subsequently immobilized on the functionalized CNT and CNT/polyethylene composite was prepared via in-situ ethylene polymerization. The polymerization activities of metallocene supported on CNT functionalized with glycine and benzaldehyde (Gly+BA-CNT) were similar to those of metallocene supported on CNT functionalized with N-benzyloxycarbonylglycine and paraformaldehyde (Z-Gly+PFA-CNT) although its Zr content was lower than that of Z-Gly+PFA-CNT. In the case of metallocene supported on Z-Gly+PFA-CNT, the even distribution of active sites hindered the diffusion of ethylene monomer and cocatalyst MAO due to steric hindrance during ethylene polymerization. Compared to polyethylene produced from homogeneous metallocene catalysts, CNT/PE composites had a higher initial degradation temperature ($T_{onset}$) and maximum mass loss temperature ($T_{max}$). It suggests that pyrrolidine functionalized CNT is uniformly dispersed and strongly interacted with the PE matrix, enhancing the thermal stability of PE.

• Elastomers and Composites
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• v.48 no.4
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• pp.269-275
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• 2013

In this study, we prepared poly(ethylene-ter-1-hexene-ter-divinylbenzene) using various metallocene catalysts with trityl tetrakis(pentafluorophenyl)borate/triisobutylaluminium cocatalysts system. We tried rac-$Et(Ind)_2ZrCl_2$, rac-$SiMe_2(Ind)_2ZrCl_2$, and rac-$SiMe_2(2-Me-Ind)_2ZrCl_2$ to choose optimum metallocene catalyst, comparing with catalytic activity, molecular weight, molecular weight distribution of the terpolymers. To study the effects of chain length of high ${\alpha}$-olefins on the terpolymerization, we synthesized the terpolymers using 1-hexene, 1-octene, 1-decene or 1-dodecene. We characterized chemical composition, thermal properties, and mechanical properties of the terpolymers.

• Polymer(Korea)
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• v.24 no.4
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• pp.445-452
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• 2000

The copolymerization of ethylene (E) and norbornene (N) was examined by using various metallocene catalysts and modified-MAO(MMAO) cocatalyst. For $C_2$-symmetry catalysts such as rac-Et(Ind)$_2$ZrC $l_2$, M $e_2$Si(Ind)$_2$ZrC $l_2$, M $e_2$Si(Cp)$_2$ZrC $l_2$ and Cs-symmetrical iPr(FluCp)ZrC $l_2$ as well as CGC and di-bridged zirconocene, the effects of catalyst structure and [N]/[E] feed ratio on catalyst activity, thermal property and [N] content of copolymer (COC) was investigated. For rac-Et(Ind)$_2$ZrC $l_2$ catalyst of a constant [N]/[E] feed ratio, the appropriate conditions of [Al]/[Zr] mole ratio, polymerization temperature and cocatalyst structure were found to be 3000, 4$0^{\circ}C$, MMAO cocatalyst, respectively. As [N]/[E] feed ratio increased, the incorporation of norbornene to copolymer increased while, the activity of catalyst decreased except for iPr(FluCp)ZrC $l_2$ With consideration of catalyst activity as well as N content, it was found that rac-Et(Ind)$_2$ZrC $l_2$/MMAO system exhibited relatively high activity and controllable $T_{g}$. Monomer reactivity ratio was determined by Kelen-Tudos method..

• Elastomers and Composites
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• v.48 no.4
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• pp.263-268
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• 2013

In this study, we prepared poly(ethylene-ter-1-hexene-ter-divinylbenzene) using bridged rac-$Et[Ind]_2ZrCl_2$ metallocene catalysts. The effect of 1-hexene on the terpolymerization rate was evaluated. When cocatalyst/catalyst molar ratio was 3,000, catalytic activity indicated more than 8,000 which was very remarkable value. As polymerization time increased, the weight-average molecular weight of the terpolymer gradually increased to some degree. In case of a polymerization time of 50 minutes, the terpolymer became amorphous state. The molecular weight distribution and densities of the terpolymer were 110,000-200,000 and $0.85-0.89g/cm^3$, respectively. Thermal properties and structure of the terpolymer were also identified.

• Korean Chemical Engineering Research
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• v.53 no.3
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• pp.397-400
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• 2015

The effects of surface treatment method of unreacted N-[3-(trimethoxysilyl)propyl]ethylenediamine (2NS), $N^1$-(3-trimethoxysilylpropyl)diethylenetriamine (3NS), and 3-cyanopropyltriethoxysilane (1NCy) after grafting on the surface of silica and of the surface treatment temperature on ethylene polymerization were investigated. The Zr content of supported catalyst employing filtering method was higher than that of washing method, and the activities of supported catalysts prepared by washing method were higher than those of filtering methods significantly. Regardless of surface treatment methods the activities were in order by $SiO_2/2NS/(n-BuCp)_2ZrCl_2>SiO_2/1NCy/(n-BuCp)_2ZrCl_2>SiO_2/3NS/(n-BuCp)_2ZrCl_2$. The ethylene polymerization activity was increased as the surface treatment temperature of aminosilane on silica increased.

• Elastomers and Composites
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• v.48 no.1
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• pp.2-9
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• 2013

We synthesized polyethylene, poly(ethylene-co-1-decene), poly(ethylene-co-p-methylstyrene), and poly(ethylene-ter-1-decene-ter-p-methystyrene) using a rac-$Et(Ind)_2ZrCl_2$ metallocene catalyst and a methylaluminoxane cocatalyst system. The materials were characterized using nuclear magnetic spectroscopy and fourier transform infrared spectroscopy. To identify suitable reaction conditions for terpolymerization, we studied the effects of catalyst content, cocatalyst/catalyst molar ratio, polymerization time, and polymerization temperature. As the catalyst content increased, the catalytic activity and the molecular weight of the terpolymers increased. The catalytic activity sharply increased but little change was observed after a polymerization time of 30 min. The increase in the cocatalyst/catalyst molar ratio resulted in a decrease in the molecular weight of the terpolymers and an increase in the catalytic activity to some degree. The catalytic activity increased with increasing polymerization temperature, while the molecular weight of the terpolymers decreased.

• Applied Chemistry for Engineering
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• v.29 no.4
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• pp.461-467
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• 2018

In this study, $(n-BuCp)_2ZrCl_2$, was supported on $SiO_2/MgCl_2$ binary support. Before supporting the catalyst, the $SiO_2/MgCl_2$ binary support was surface treated with three different alkyl aluminum compound, namely trimethylaluminum, triethylaluminum, and ethylaluminum sesquichloride. The synthesized surface-treated $SiO_2/MgCl_2$ supported metallocene catalysts were used for the copolymerization of ethylene and 1-hexene. Their catalytic properties and performances were analyzed through BET, XPS analysis, ICP-AES analysis, and FE-SEM. While the resulting copolymers were analyzed through DSC analysis, GPC analysis, 13C-NMR analysis, and FE-SEM. The analysis of synthesized surface-treated $SiO_2/MgCl_2$ supported metallocene catalysts showed that the Zr content of these catalysts is relatively lower compared to that of the catalyst supported on $SiO_2$. This could be attributed to the reduction in the surface area of $SiO_2$ due to the presence of recrystallized $MgCl_2$ and alkyl aluminum. Furthermore, they exhibited a better copolymerization activity compared to that of $SiO_2$ supported catalyst, particularly the EASC-surface treated binary support, which has the highest activity of 1.9 kg PE/($mmol-Zr^*hr$) because EASC acts as a strong Lewis acid. It could also be observed that the larger the ligand of alkyl aluminum used, the rougher the particle surface of the resulting polymer.

• Macromolecular Research
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• v.15 no.5
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• pp.430-436
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• 2007

The dinuclear half-sandwich CGCs (constrained geometry catalyst) with a polymethylene bridge, $[Ti({\eta}^5 : {\eta}^1-indenyl)SiMe_2NCMe_3]_2(CH_2)_n]$[n = 6 (1) and 12 (2)], have been employed in the copolymerization of ethylene and norbornene (NBE). To compare the mononuclear metallocene catalysts; $Ti({\eta}^5 : {\eta}^1-2-hexylindenyl)SiMe_2NCMe_3$ (3), $(Cp^* SiMe_2NCMe_3)$Ti (Dow CGC) (4) and ansa-$Et(Ind)_2ZrCI_2$ (5), were also studied for the copolymerization of ethylene and NBE. It was found that the activity increased in the order: 1 < 2 < 3 < 5 < 4, indicating that the presence of the bridge between two the CGC units contributed to depressing the polymerization activity of the CGCs. This result strongly suggests that the implication of steric disturbance due to the presence of the bridge may playa significant role in slowing the activity. Dinuclear CGCs have been found to be very efficient for the incorporation of NBE onto the polyethylene backbone. The NBE contents in the copolymers formed ranged from 10 to 42%, depending on the polymerization conditions. Strong chemical shifts were observed at ${\delta}$42.0 and 47.8 of the isotactic alternating NBE sequences, NENEN, in the copolymers with high NBE contents. In addition, a resonance at 47.1 ppm for the sequences of the isolated NBE, EENEE, was observed in the $^{13}C-NMR$ spectra of the copolymers with low NBE contents. The absence of signals for isotactic dyad at 48.1 and 49.1 ppm illustrated there were no isotactic or microblock (NBE-NBE) sequences in the copolymers. This result indicated that the dinuclear CGCs were effective for making randomly distributed ethylene-NBE copolymers.

• Polymer(Korea)
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• v.36 no.1
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• pp.111-116
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• 2012

A functionalization of mesoporous materials with organosilane was carried out via a post-synthesis grafting method and $(n-BuCp)_2ZrCl_2$/methylaluminoxane (MAO) as subsequently immobilized on the functionalized mesoporous materials for ethylene polymerization. Organosilanes having amine, cyano or imidazoline group such as $N$-[(3-trimethoxysilyl)propyl]ethylenediamine (2NS), 4-(triethoxysilyl)butyronitrile (1NCy), 1-(3-triethoxysilylpropyl)-2-imidazoline (2NIm) were used for the surface functionalization of mesoporous materials. In the SBA-15/2NS/$(n-BuCp)_2ZrCl_2$ catalyst preparation, the amount of MAO in feed increased with an decrease in the Zr content of the supported catalyst, and Al content in the supported catalyst increased. The ethylene homopolymerization activity of SBA-15/2NS/$(n-BuCp)_2ZrCl_2$ dramatically increased as the amount of MAO in feed increased. Furthermore, when the immobilization time was 6 hrs, SBA-15/2NS/$(n-BuCp)_2ZrCl_2$ showed the highest activity. The activities of supported 2NS-, 1NCy-, 2NIm-functionalized catalysts decreased in the following order, SBA-15/2NS/ > SBA-15/2NIm/ > SBA-15/1NCy/$(n-BuCp)_2ZrCl_2$. 2NS and 2NIm which have two amine groups per silane molecule were shown to interact with $(n-BuCp)_2ZrCl_2$ strongly compared to 1NCy which has one amine group. Thus, the activities increased with an increase in the nitrogen and the Zr content of the supported catalysts.