Abstract
Porous organic polymers (POPs) are widely used in various areas such as adsorption, separation and catalysis. In the present work, ionic liquid-modified porous organic polymers (IL-POPs) synthesized by dispersion polymerization were applied to immobilize metallocene catalysts for olefin polymerization. The prepared IL-POPs were characterized by Fourier transform infrared spectrometer (FT-IR), nitrogen sorption porosimetry, X-ray photoelectron spectroscopy (XPS), thermal gravimetric analysis (TGA), inductively coupled plasma atomic emission spectrometer (ICP) and scanning electron microscope (SEM) analysis. The IL-POPs obtained pores with surface specific area (SSA) ranging from 16.9 m2/g to 561.8 m2/g, and total pore volume (TPV) ranging from 0.08 cm3/g to 0.71 cm3/g. The supported catalysts Zr/MAO@IL-POPs exhibit great activity (3700 kg PE/mol·Zr·bar·h) in ethylene polymerization, and the GPC-IR results show that the polyethylene has narrow molecular weight distribution (2.2 to 2.8). The DSC results show that the melting point of prepared polyethylene was as high as 138 °C, and the TREF analysis results indicate that they have similar chemical composition distribution with elution temperature at 100.5–100.7 °C.
Highlights
Since Kaminsky and Sinn discovered polymerization activity could be greatly improved by methylaluminoxane (MAO), the manufacture of metallocene polyolefins with controlled chain structure and narrow molecular weight distribution developed rapidly, and the metallocene and post-metallocene catalysts attract great attention of chemists [1–5]
Considering that the typical ionic composition of ionic liquids (ILs) may have a positive effect on MAO/metallocene immobilization, we introduce 1-butyl-3-vinylimidazolium-chloride ([BVIM] [Cl]) as a functional comonomer for the synthesis of mono-functional-group and dual-functional-group IL-Porous organic polymers (POPs)
It can be seen from the IR spectrum (Figure 6) that the hydroxyl bands of supported catalysts disappeared after MAO pretreating, and the broad and strong bands of Zr/MAO@ionic liquid-modified porous organic polymers (IL-POPs) system at 683 cm−1 assigned to Al-O stretching vibration, confirming that MAO cages were successfully immobilized on IL-POPs [32]
Summary
Since Kaminsky and Sinn discovered polymerization activity could be greatly improved by methylaluminoxane (MAO), the manufacture of metallocene polyolefins with controlled chain structure and narrow molecular weight distribution developed rapidly, and the metallocene and post-metallocene catalysts attract great attention of chemists [1–5]. The metallocene/MAO catalysts should be immobilized on support to avoid reactor fouling, to help control the morphology of polymer particles and to reduce the cost of cocatalyst [6,7]. Wioletta et al used ionic liquid-modified silica (SIL)-supported metallocene to catalyze ethylene polymerization and obtained linear polyethylene with a high melting temperature and crystallinity, proving that the ionic liquid could be used as an olefin polymerization catalyst component [29]. Considering that the typical ionic composition of ILs may have a positive effect on MAO/metallocene immobilization, we introduce 1-butyl-3-vinylimidazolium-chloride ([BVIM] [Cl]) as a functional comonomer for the synthesis of mono-functional-group and dual-functional-group IL-POPs. The prepared IL-POPs obtained good porosity, and the pore structure can be modulated by adjusting the comonomer contents and solvent system. Poloxamer 407 (F127, BASF), zirconocene ((n-BuCp)2ZrCl2), DALCHEM, Nizhny Novgorod, Russia) and other reagents were used directly as received
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