# Porous Organic Polymers-Supported Metallocene Catalysts for Ethylene/1-Hexene Copolymerization
## 2 Results and Discussion  
### Pore Structure of POPs and POPs-Supported Metallocene Catalysts  
In this work, several POPs (POP-1/POP-2/POP-3) were preparedin 2-methyl-1-propanol, ethanol/deionized water (volume ratio = 9:1), and ethyl acetate, respectively, according to a dispersion polymerization method [30]. Then, the prepared POPs were used as metallocene catalyst supports to obtain POPs-supported metallocene catalysts. The pore structure of the POPs and the POPs-supported metallocene catalysts were characterized with a Nova 2000e instrument;the porosity parameters results are shown in Table 1. In a previous paperwe showed [32] that the pore structure of the immobilized metallocene catalyst is highly dependent on the pore structure of the POPs with similar pore size distributions, except that a mild left shift of pore size and decrease of abundance of pore size are observed on the supported metallocene catalysts due to the non-covalent bonding of zirconocene complex/MAO to the POPs. From Table 1, we can see that the prepared POPs obtained different pore structures, with pore diameter ranging from 4 nm to 12 nm, specific surface area (SSA) ranging from 300 m\({}^{2}\)/g to 450 m\({}^{2}\)/g, and the supported metallocene catalysts also obtained similar pore structure with a mild decrease of average pore size ranging from 3 nm to 11 nm, as mentioned above. However, compared with the POPs and POPs-supported metallocene catalysts, a dramatic decrease of average pore size of silicafrom 21.0 nm to 9.68 nm was observed when silica 2408 was used as the metallocene support. This shows that the prepared POP supports have better pore structure stability than inorganic silica as metallocene catalyst support. The nitrogen sorption isotherms of the three POPs and silica 2408 are shown in Figure 1a. From the curves we can observe that very different porous structures were obtained. In order to investigate how the pore structure of the POPs influenced the chain growth of the ethylene/1-hexene copolymer, non-local density functional theory (NLDFT) simulation was adopted to determine the pore size distribution using N\({}_{2}\)-carbon kernel at 77 K based on a slit-pore model. As shown in Figure 1b,c, the pore size and the pore size distribution of three POP supports (POP-1/POP-2/POP-3) varied greatly due to the different solvent parameters of the three types of solvents. However, despite the different pore size distribution, a similarity exists in the pore structure of the three POP supports, such that high abundance in the pore size of 1-4 nm scale can be observed in their NLDFT curves. Furthermore, the pore size distribution of the HEMA-functionalized POPs could be easily controlled by the selection of different HEMA/divinylbenzene (DVB) molar ratio or different solvent [29; 30]. In contrast, the pore sizes of silica 2408 mainly focused in the meso-pore range (roughly 6-30 nm). \begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Entry** & **Sample** & \begin{tabular}{c} **Specific Surface Area** \\ **(Multi Point BET) (m\({}^{2}\)/g)** \\ \end{tabular} & \
\begin{tabular}{c} **Total Pore Volume** \\ **(cm\({}^{3}\)/g)** \\ \end{tabular} &
\begin{tabular}{c} **Average Pore** \\ **Diameter(nm)** \\ \end{tabular} \\ \hline
1-1 & POP-1 & 427 & 0.655 & 6.14 \\
1-2 & BCZ/MAO@POP-1 & 299 & 0.318 & 4.26 \\
2-1 & POP-2 & 414 & 0.416 & 4.02 \\
2-2 & BCZ/MAO@POP-2 & 261 & 0.219 & 3.36 \\
3-1 & POP-3 & 318 & 0.893 & 11.2 \\
3-2 & BCZ/MAO@POP-3 & 288 & 0.730 & 10.1 \\
4-1 & Silica-2408 & 279 & 1.47 & 21.0 \\
4-2 & BCZ/MAO@Silica-2408 & 272 & 0.658 & 9.68 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Characterization data of P(HEMA-co-DVB) particles and (_n_-BuCp)\({}_{2}\)ZrCl\({}_{2}\)/MAO/POPs metallocene catalysts (BCZ/MAO@POPs) from N\({}_{2}\) sorption results.BET: Brunauer–Emmett–Teller; HEMA: 2-hydroxyethylmethacrylate; MAO: methylaluminoxane; POP: porous organic polymer. Figure 1: (a) N\({}_{2}\) isotherms.