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Polyolefin-nanocomposites with special properties by in-situ polymerization

Walter Kaminsky

《化学科学与工程前沿（英文）》 2018年第12卷第3期页码 555-563 doi: 10.1007/s11705-018-1715-x

摘要：

Exceptionally strong polyolefin nanocomposites are synthesized by in-situ polymerization using soluble metallocene/methylaluminoxane (MAO) as catalysts in a two-step process. First, the soluble metallocene/MAO or other single site catalysts are absorbed on the surface of the nanofillers. Then by addition of ethene or propene, a polyolefin film is formed, covering the nanoparticles, layered silicates, or fibers. The resulting polyethylene and polypropylene nanocomposites are characterized by better physical and chemical properties such as stiffness, gas barrier properties, degradation temperatures, and crystallization rates. They show better mechanical properties than materials produced by mechanical blending. The thickness of the polyolefin can be controlled by the pressure of ethene or propene and by the polymerization time. Carbon fibers and carbon nanotubes are covered with isotactic or syndiotactic polypropylene. Because of the hydrophobic character of the carbon surface, the polymer is drawn on the fiber. This leads to a reinforced combined polymer with special properties. The crystallization temperature is 10 °C higher and therefore the crystallization rate up to 20 times faster than that of pure syndiotactic polypropylene. The form stability increases by 100% if 3 wt-% of carbon nanotubes are incorporated.

关键词： polyolefin nanocomposites metallocenes methylaluminoxane

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Polymerization of methyl methacrylate catalyzed by mono-/bis-salicylaldiminato nickel(II) complexes and methylaluminoxane

Jihong LU, Danfeng ZHANG, Qian CHEN, Buwei YU

《化学科学与工程前沿（英文）》 2011年第5卷第1期页码 19-25 doi: 10.1007/s11705-010-0546-1

摘要： Two types of salicylaldiminato-based nickel complexes, mono-ligated Ni(II) complexes ([O-C H - - C(H)=N-Ar]Ni(PPh )(Ph) ( ), [O-(3,5-Br )C H - -C(H)=N-Ar]Ni(PPh )(Ph) ( ), [O-(3- -Bu)C H - -C(H)=N-Ar]Ni(PPh )(Ph) ( )) and bis-ligated Ni(II) complexes ([O-(3,5-Br )C H - -C(H)=N-Ar] Ni ( ), [O-(3,5-Br )C H - -C(H)=N-2-C H (PhO)] Ni ( ), Ar=2,6-C H ( -Pr) ) were synthesized and characterized by Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), mass spectrography (MS) and elemental analysis (EA). In the presence of methylaluminoxane (MAO) as cocatalyst, all the nickel complexes exhibited high activities for the polymerization of methyl methacrylate (MMA) and syndiotactic-rich poly(methyl methacrylate) (PMMA) was obtained. The complexes with less bulky substituents on salicylaldiminato framework possessed higher activities, while with the same salicylaldiminato, the mono-ligated nickel complexes showed higher catalytic activity than bis-ligated ones.

关键词： late transition metal catalyst methyl methacrylate polymerization salicylaldiminato nickel complexes methylaluminoxane syndiotactic structure