倍半硅氧烷
催化作用
聚乙烯
分子
聚合
X射线光电子能谱
吸附
高分子化学
结晶
扩散
化学
化学工程
傅里叶变换红外光谱
材料科学
聚合物
物理化学
有机化学
工程类
物理
热力学
作者
Zhen Yue,Ning Wang,Yu Cao,Wei Li,Cheng‐Di Dong
标识
DOI:10.1021/acs.iecr.9b06780
摘要
The polyhedral oligomeric silsesquioxane (POSS)-modified Ziegler–Natta catalysts with judicious immobilization of TiCl4 were synthesized for ethylene polymerization. The structure of active sites in this heterogeneous catalyst was investigated by X-ray photoelectron spectroscopy, CO low-temperature adsorption diffusion reflectance infrared Fourier transform (DRIFT) spectra, and density functional theory calculations. The incorporated POSS molecules contribute to the formation of the MgCl2 (110) plane, creating more positions for hosting the active sites. Simultaneously, POSS induced the crystallization of MgCl2 molecules, and the latter capture the deactivated TiCl4 molecules and consume part of the loaded TiCl4. This combination dilutes the active sites on the catalytic surface and gives rise to more isolated active species and results in enhanced catalytic activity and decrement of the chain overlap. As a result, the ultrahigh-molecular-weight polyethylene (UHMWPE) with a less entangled state was successfully synthesized at 80 °C, with exceptional activity (6.18 × 105 g PE molTi–1 h–1 bar–1). The synthesized UHMWPE presents less morphological defects after the fusion, thanks to the weakly entangled state, and shows a pronounced improvement of the impact property.
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