## 3 Results and Discussion  
### Preparation of the PolyHIPE Materials  
#### 3.1.1 The W/O Ratio  
The W/O ratio is one of the most important parameters that has a great influence on the HIPE stability, which contributes to the structure of the resultant polyHIPE materials. Figure 2 showed the typical SEM images of the polyHIPE materials prepared with different W/O ratio. All the polyHIPE materials exhibited open-cellular porous structures. Much larger open voids and interconnected \"windows\" could be observed upon the W/O ratio increasing from 80/20 to 90/10. The average sizes of the voids were 6.5 \(\upmu\)m, 11.2 \(\upmu\)m and 12.0 \(\upmu\)m for the polyHIPE scaffolds prepared with W/O ratio of 80/20, 85/15 and 90/10, respectively, which were listed in Table 2 (Formulations 1-3). The mercury intrusion porosimetry results in Figure 3 showed that the total pore volume of the polyHIPE materials increased from 7.02 to 9.61 mL/g while the W/O increased from 80/20 to 90/10. The pore size of the interconnected \"windows\" sharply increased from 0.31 \(\upmu\)m to 2.61 \(\upmu\)m while the percentage of inner aqueous phase increased from 80% to 90%, as shown in Table 2. From the mercury intrusion porosimetry data, the porosity for the polyHIPE materials prepared with different W/O ratios was as high as 89.8-95.3%. The increases in the size of voids and \"windows\", as well as the pore volume and porosity were likely due to the fact that large droplets could be formed at a higher W/O ratio. As the water fraction increases, the surfactant must stabilize an increasingly large water-oil interfacial area. With a decrease the water-oil interfacial area, the average water droplet size would greatly increase, which resulted in an increase in the void size of the resultant polyHIPE materials with a higher W/O ratio. Meanwhile, the skeletal framework (continuous phase in HIPE) of the solid poly(St-DVB) became progressively thinner, which resulted from the concomitant thinning of the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Formulation** & **BET Surface** & **Pore Volume** & **Pore Volume** & **Posvity (\%) a** & **D (\(\upmu\)) b** & **D (\(\upmu\)) c** & **Dw (\(\upmu\)) d** \\
**No.** & **Area (m\({}^{2}\)/g)** & **(mL) a** & **Pore Volume** & **Pore Volume** & **Pore Volume** & **Pore Volume** & **Pore Volume** \\ \hline
1 & 30.5 & 7.02 & 89.8 & 6.5 & 0.31 & 15.2 \\
2 & 26.5 & 8.49 & 94.8 & 11.2 & 2.00 & 19.0 \\
3 & 24.6 & 9.61 & 95.3 & 12.0 & 2.61 & 21.5 \\
4 & 23.7 & 9.08 & 86.4 & 15.8 & 2.56 & 23.2 \\
5 & 6.3 & 6.15 & 87.9 & 23.7 & 0.60 & 58.6 \\ \hline \hline \end{tabular}  
* Pore volume and porosity determined by Hg mercury intrusion porosimetry; b Average void diameter determined by SEM; c Average interconnected window diameter determined by Hg mercury intrusion porosimetry; d Pore size (Dw) obtained from the BjH treatment of N\({}_{2}\) adsorption data.  
\end{table} 
Table 2: Characterization of the polyHIPE materials. Figure 2: SEM images of PolyHIPE scaffolds fabricated with W/O ratio of (**a**) 80/20, (**b**) 85/15 and (c) 90/10. continuous phase film around the aqueous droplets. Thus, the increase of the water fraction resulted in an increase in the size of \"windows\". Figure 4 showed the nitrogen adsorption-desorption curves of the polyHIPE materials with varied W/O ratio. The BET surface areas, as cumulated with the nitrogen adsorption isotherms, were 30.5 m\({}^{2}\)/g, 26.5 m\({}^{2}\)/g and 24.6 m\({}^{2}\)/g for the polyHIPE materials prepared with W/O ratio of 80/20, 85/15 and 90/10, respectively. A slight decrease in the BET surface area was observed with the W/O ratio increased. The average pore sizes of \(<\)Dw\(>\), which were obtained from BJH treatment the of nitrogen adsorption data, were 15.2 nm, 19.0 nm and 21.5 nm for the polyHIPE materials with an increased W/O ratio, respectively. The changes of BET surface area and \(<\)Dw\(>\) likely resulted from the phase separation in the polymerization process.