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  • 저자

    이정숙

  • 학위수여기관

    공주대학교 대학원

  • 학위구분

    국내박사

  • 학과

    화학공학과

  • 지도교수

    고영수

  • 발행년도

    2014

  • 총페이지

    viii, 125장

  • 키워드

    graphene metal-organic frameworks(MOFs) metallocene polymerization;

  • 언어

    kor

  • 원문 URL

    http://www.riss.kr/link?id=T13532676&outLink=K  

  • 초록

    In this study, the effect of various nano-space confining single-site catalyst and methylaluminoxane (MAO) on ethylene-1-hexene and propylene-1-hexene copolymerization behaviors as well as on the microstructure of the resulting polymer was investigated in detail. Carbon-based nanomaterials such as multilayer graphene (MLG) and metal-organic frameworks (MOFs) were used as catalyst support and nanofillers for ethylene or propylene polymerizations. The MLG-supported (n-BuCp)₂ZrCl₂ catalyst system produced polyethylene with extremely high molecular weight (MW), much higher than the MW of polyethylene from unsupported (n-BuCp)₂ZrCl₂ catalyst. We suggest that MLG can serve not only as a support for adsorption but also as an additional ligand to (n-BuCp)₂ZrCl₂ during ethylene polymerization. The surface of graphene can be a strong and bulky ligand that is attached to (n-BuCp)₂ZrCl₂ . The β-hydrogen elimination mechanism can be disturbed by the bulky surface of graphene. The initial degradation temperature (T_(onset)) for the MLG/polyolefin nanocomposites increased by about 20 ℃ compared with neat polyolefin, and maximum mass loss temperature (T_(max)) increased by about 7 ℃. It means the presence of graphene definitely improve thermal stability of polyolefin when it is dipsersed in the polymer matrix. Nano-dispersed MLG can act as barriers to hinder the heat transfer within the MLG/polyolefin nanocomposites, which would shift to higher degradation temperature. The shape and size of nanopore of metal-organic frameworks (MOFs) influenced on the behaviors of ethylene-1-hexene copolymerization in terms of the microstructure of the resulting polymer. In the cases of ZIF-8 and MIL-53 having the smaller pore size, the metallocene was present on the outer surface of supports. In the cases of DETA-MIL-101 and MIL-101 having the larger pore relative to ZIF-8 and MIL-53, the metallocene was confined inside the nanopore of MIL-101. 1-Hexene contents of every copolymers prepared with DETA-MIL-101 and MIL-101 supported (n-BuCp)₂ZrCl₂ catalysts was almost nil though the C_(6)/C₂ molar ratio in feed increased from 0.0 to 4.4. Incorporation into the growing polyethylene chain of 1-hexene having large kinetic diameter relative to ethylene is hindered because of the small diameter during ethylene-1-hexene copolymerization. The shape-selective polymerization occurred with DETA-MIL-101 and MIL-101 supported (n-BuCp)₂ZrCl₂ catalysts due to the restricted smaller nanopore. The DETA-MIL-101 supported catalyst produced the narrower polydispersity index (PDI) but the larger MW. The presence of DETA resulted to more homogeneous active sites compared to the absence of DETA. MIL-53/MAO/Me₂Si(2-Me-4-PhInd)₂ZrCl₂ polymerized propylene with higher activity and higher molecular weight than SBA-15 or SiO₂/MAO/Me₂Si(2-Me-4-PhInd)₂ZrCl₂. The active sites can be surrounded by AlO_(6)-octahedral of SBU, and the steric hindrance of AlO_(6)-octahedral made β-hydrogen elimination difficult, resulting in higher molecular weight.


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