## 2 Results and Discussion
### Polymerisation of Polystyrene-co-Divinylbenzene PolyHIPEs in Silcosteel Tubing  
Before fabricating a PS-_co_-DVB polyHIPE in silcosteel tubing (this monolith being likely to have a more permeable pore morphology relative to the GMA-_co_-EDMA polyHIPE), some preliminary experiments were first conducted to investigate the effect of aqueous phase ratios upon pore size and surface area. Therefore, 75%, 80% and 90% PS-_co_-DVB bulk polyHIPEs were produced and characterised using scanning electron microscopy (SEM) and Brunauer-Emmett-Teller(BET) surface area analysis. As expected, when the aqueous phase percentage was decreased, the pore morphology also changed. Specifically, the number of interconnecting windows between the larger voids decreased when the aqueous phase percentage was decreased, and this finding is in keeping with reports from the [PERSON] group [25; 46; 47]. Furthermore, as the aqueous phase ratio decreased, the voids also decreased in size from 12.9 \(\pm\) 1.9 \(\upmu\)m for the 90% polyHIPE, to 10.4 \(\pm\) 2.5 \(\upmu\)m for the 80% polyHIPE and 7.5 \(\pm\) 1.0 \(\upmu\)m for the 75% polyHIPE (\(n\) = 30 in each case), again in keeping with literature reports [25; 46; 47]. This represents a 42% decrease in average pore size between the two extremes of porosity under investigation in this study and would be expected to result in an increase in surface area. Indeed, surface areas were 20.1 m\({}^{2}\). g\({}^{-1}\), 24.3 m\({}^{2}\). g\({}^{-1}\) and 23.3 m\({}^{2}\). g\({}^{-1}\) for the 90%, 80% and 75% polyHIPEs respectively, corresponding to a 16% increase in surface area from the 90% polyHIPE to the 75% polyHIPE; these surface areas and the general increasing trend are typical for this type of polyHIPE [29]. Since the increase in surface area for the lower porosity monolith was only slight, the 90% polyHIPE formulation was selected for further studies in silcosteel column formats due to the anticipated higher permeability because of the larger flow-through void sizes. A larger diameter silcosteel tube (2.2 mm i.d.) was first trialled with the 90% polyHIPE formulation, but no monolith formed at 60 \({}^{\circ}\)C. Even after 48 h of incubation time, the still liquefied emulsion was easily extruded from the column with a solvent flush, and after increasing the polymerisation temperature to 75 \({}^{\circ}\)C, a glass-like polymer adhered to the inner walls only, leaving a large gap through the central bore of the column. For this reason, the use of 2.2 mm i.d. housings was rejected in favour of 1.0 mm i.d. tubing. It should be noted that polyHIPEs have been fabricated in housings as large as 11 mm i.d. [48], however these reports are for oligo(ethylene-glycol)methacrylate-_co_-GMA-_co_-EDMA polyHIPEs with an obviously very different formulation than the one described herein, and the polyHIPE housing was a glass vial rather than a metal housing. [PERSON] _et al._ formed methacrylate monoliths in a 0.8 mm i.d. titanium housing and were forced to utilize a complex temperature gradient during polymerisation to minimize the occurance of a radial gradient of monolith density across the column diameter [42]. This counteracted the inability of the polymerisation system to effectively dissipate the heat of polymerisation, a phenomenon reportedas early as 1997 by [PERSON] _et al._[49] and further examined in detail by [PERSON] _et al._[30; 50], and [PERSON] _et al._[34]. However, no such gradient requirement was necessary for the polyHIPE fabrication in 1.0 mm i.d silcosteel tubing. The polyHIPE exhibited excellent adhesion to the column housing (Column #1) as shown in Figure 2a,b. Some polyHIPE debris seen in Figure 2a was unavoidable due to cutting the tubing for SEM imaging, despite backflushing with water in attempts to remove it.