• Journal of the Korean Applied Science and Technology
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• v.33 no.2
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• pp.247-254
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• 2016

Since microzirconia has excellent thermal and mechanical properties with high chemical and electrical resistance, it can be used in various fields. When the surface of zirconia becomes hydrophilic, its dispersibility in water will be improved as well as the resistance to most hydrophobic contaminants will be increased. In this study, we investigated the introduction of a hydrophilic groups on the microzircornia surface through hydrolysis and condensation reactions with two different silanes containing hydrophilic functional groups, such as ${\gamma}$-aminopropyltrimethoxysilane (APS) and ${\gamma}$-ureidopropyltrimethoxysilane (UPS) at different pH and concentration conditions. A covalent bond formation between the surface hydroxyl groups of zirconia and that of hydrolyzed silanes was confirmed by ninhydrin test and FT-IR spectroscopy. However, the presence of Si on the surfaces of both silane modified microzirconias was unable to detect by SEM/EDS technique. In addition, particle size analysis results provide that the size of microzirconia was changed to smaller or bigger than that of original zirconia due to crushing and aggregation during the modification process. The water dispersibility was improved for only APS modifed zirconia (AS-2 and AS-3) under neutral pH condition, but the water dispersibility and stability for all cases of 0.5~2% UPS modifed zirconia (US series) were much improved.

• Applied Chemistry for Engineering
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• v.27 no.3
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• pp.313-318
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• 2016

In this study, an amorphous silica was functionalized with aminosilane, N-[(3-trimethoxysilyl)propyl]ethylenediamine (2NS) and the late transition metal catalysts including ($(DME)NiBr_2$ and $PdCl_2$(COD)) were subsequently immobilized on the functionalized amorphous silica for norbornene polymerization. Effects of the polymerization temperature, polymerization time, Al/Ni molar ratio, and type of co-catalyst on norbornene polymerization were investigated. Unsupported late transition metal catalysts did not show any activities for norbornene polymerization. However, the $SiO_2$/2NS/Ni catayst with MAO system, with increasing polymerization temperature, increased the polymerization activity and decreased the molecular weight of the polynorbornene (PNB). Furthermore, the catalyst when increasing polymerization temperature caused the decrease in both the polymerization activity and molecular weight of PNB. This confirmed that the stability of $SiO_2$/2NS/Ni at a high temperature was greater than that of $SiO_2$/2NS/Pd. Also the longer polymerization time resulted in the higher conversion of norbornene for both catalysts. When the Al : Ni molar ratio was 1000 : 1, the highest activity (15.3 kg-PNB/($({\mu}mol-Ni^*hr$)) but lowest molecular weight ($M_n$ = 124,000 g/mol) of PNB were achieved. Also $SiO_2$/2NS/Ni catalyst with borate/TEAL resulted in diminishing the polymerization activity and molecular weight of PNB with increasing the polymerization temperature.

• Applied Chemistry for Engineering
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• v.25 no.4
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• pp.396-400
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• 2014

The pore surface of mesoporous materials, SBA-15 and MCM-41 were functionalized with organosilanes, 3-aminopropyltrimethoxysilane (1NS) and N-[(3-trimethoxysilyl)propyl]ethylenediamine (2NS) via grafting method. $(n-BuCp)_2ZrCl_2$ and methylaluminoxane (MAO) were impregnated on the surface-functionalized mesoporous materials for the application to ethylene polymerization. In the case of SBA-15/2NS/$(n-BuCp)_2ZrCl_2$ supported Zr and Al contents decreased as grafted 2NS content increased. However, in the case of MCM-41/2NS/$(n-BuCp)_2ZrCl_2$ supported Al content decreased, but Zr content increased as grafted 2NS content increased. The polymerization activity of SBA-15/2NS/$(n-BuCp)_2ZrCl_2$ increased as the amount of grafted 2NS increased. Increase in the amount of grafted 2NS should caused decrease in pore volume and diameter. Consequently, it decreased the amount of supported metallocene and MAO in general. However, the smaller pore-sized MCM-41 could have lower supported MAO content due to its large molecular size in case that MCM-41 was surface-functionalized with 2NS. Therefore, the supported metallocene content could increase and its polymerization activity was higher than that of SBA-15.