# Ionic Liquid-Modified Porous Organic Polymers as Efficient Metallocene Catalyst Supports
## 3 Results and Discussion
### Characterization of Prepared Polyethylene  
As can be seen from Table 3, IL-POPs-supported catalysts exhibited a high activity in ethylene polymerization, and the obtained PEs reveal a narrow distribution (2.2-2.8) with the weight average molecular ranging from 18.3 \(\times\) 10\({}^{4}\) to 28.7 \(\times\) 10\({}^{4}\) g/mol. The metallocene compound anchored on the IL-POPs forms an identical active site [(n-BuCp)\({}_{2}\)ZrCH\({}_{3}\)]\({}^{+}\), and the polymer chains grow on the same active site, then polymers with narrow PDI were obtained as a result [5]. While polyethylene chains crystallize, the CH\({}_{2}\)-CH\({}_{2}\) bond rotates rapidly, and the polyethylene chains fold several times to form lamellae in which the distance between two adjacent chains is about 4.4 to 4.6 A. The melting temperature (T\({}_{m}\)) and crystallinity (\(X_{C}\)) of polyethylene can be analyzed by differential scanning calorimetry (DSC), as shown in Figure 7a, the melting curves of samples were recorded after crystallizing and annealing. It is surprising that the prepared PEs melt at a high temperature of 138 \({}^{\circ}\)C, about 4 \({}^{\circ}\)C higher than the ones that prepared by p(DVB-co-HEMA)-supported Zr/MAO catalysts with T\({}_{m}\) at 132-134 \({}^{\circ}\)C [17]. Crystallinity can be calculated by the formula \(X_{C}=\Delta H_{m}/\Delta H_{m}^{0}\), where \(X_{C}\) is the crystallinity, \(\Delta H_{m}\) is the melting endothermic enthalpy that can be integrated and calculated according to the area under the melting curve, and \(\Delta H_{m}^{0}\) which is equal to 293.0 J/g, is the melting endothermic enthalpy of polymer with 100% crystallinity. The calculated \(X_{C}\) values of PE-1, PE-3 and PE-4 are above 60%, whereas the \(X_{C}\) of PE-2 is only 54.0%. [PERSON] et al. [39] proposed that the formation of lamellar crystal is also restricted by the mobility of high weight chains; therefore, we infer that PE-2 with high molecular weight (Mw = 28.7 \(\times\) 10\({}^{4}\) g/mol) possesses a relatively low crystallinity. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Entry** & **Zr** & **Al/Zr** & **Cat** & **Yield** & **Activity** \\  & **(umol/g)** & **Molar Ratio** & **(mg)** & **(g)** & **(kg PE/mol\(\cdot\)Zr-bar-h)** \\ \hline Zr/MAO@POP-3 & 43.8 & 94.7 & 123 & 38.9 & 3606 \\ Zr/MAO@POP-5 & 22.9 & 55.3 & 160 & 3.67 & 499 \\ Zr/MAO@POP-9 & 38.4 & 87.3 & 144 & 35.6 & 3219 \\ Zr/MAO@POP-10 & 35.1 & 95.4 & 159 & 41.3 & 3700 \\ \hline \hline \end{tabular} Notes: Polymerization conditions: 0.40–0.45 MPa ethylene pressure in 800 mL reactor of stainless steel, 300 mL hexane, 3 mL. TEAL (10 wt% in hexane), 80 \({}^{\circ}\)C, 30 min.  
\end{table} 
Table 2: Zirconium and aluminum loading contents of Zr/MAO@IL-POPs and ethylene polymerization results. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Entry** & **Samples** & **T\({}_{m}\) (\({}^{\circ}\)C)** & **X\({}_{C}\) (DSC) (\%)** & **\(\Delta H_{m}\)(J/g)** & **M\({}_{w}\times 10^{4}\)** & **M\({}_{n}\times 10^{4}\)** & **PDI** \\ \hline Zr/MAO@POP-3 & PE-1 & 138.1 & 61.0 & 178.7 & 22.2 & 9.4 & 2.4 \\ Zr/MAO@POP-5 & PE-2 & 138.4 & 54.0 & 158.3 & 28.7 & 10.1 & 2.8 \\ Zr/MAO@POP-9 & PE-3 & 138.7 & 61.7 & 180.9 & 18.3 & 8.5 & 2.2 \\ Zr/MAO@POP-10 & PE-4 & 138.3 & 60.2 & 176.4 & 23.7 & 10.6 & 2.2 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: DSC and GPC results of PEs from IL-POPs supported Zr/MAO catalysts. Chemical composition distributions (CCDs) were investigated by temperature rising elution fractionation (TREF), and the result was shown in Table 4. It can be seen from Figure 4b that the four PEs are similar in TREF curves that the soluble fraction is less than 1.2% and the elution temperature peaks within the scope of 100.5-100.7 \({}^{\circ}\)C, indicating that PEs have similar CCDs. We infer that the CCDs of different PEs are mainly affected by the active sites loaded on the supports, the pore structure of supports has less effectiveness on the chemical composition distributions.