## 2 Results and Discussion  
### Polymerisation of Glycidyl Methacrylate PolyHIPES in Poly Etherether Ketone (PEEK) Tubing  
Initial efforts to fabricate a polyHIPE in a microbore format were based on the work of [PERSON] _et al._ who reported the fabrication of a lauryl methacrylate monolith in 1.0 mm i.d. PEEK tubing for the reversed phase separation of alkylbenzenes [35]. This involved the initial addition of methacryloyl groups to the inner surface of the PEEK to facilitate covalent attachment of the monolith to the column housing. Although [PERSON] _et al._ worked with a reversed phase monolith, in this work we elected in the first instance to prepare a GMA-_co_-EDMA polyHIPE using an emulsion formulation described by [PERSON] _et al._[36]. The main advantage of GMA as functional monomer is that the pendant epoxy groups on the pore surface render this monolith reactive [37] such that the surface chemistry and thus chromatographic selectivity can be tailored to a particular application; indeed, [PERSON] _et al._ reported the facile functionalisation of GMA-_co_-EDMA polyHIPEs formed within CIM disk housings (3 mm \(\times\) 12 mm i.d.) with diethylamine for the ion-exchange separation of selected proteins [36]. The authors prepared a range of GMA-_co_-EDMA polyHIPEs wherein the aqueous phase volume % was varied during emulsion preparation (60%, 75%, 80% and 90%) and they reported corresponding increases in average pore size. However, their monoliths also exhibited a very wide distribution of void sizes, with several large crater-like pores present (~10 times larger than the average void size),which increased both in size and number as the aqueous phase volume % increased. In our hands, the same phenomenon was noted, and so efforts to eliminate this effect by variation of aqueous phase volume % were deemed redundant. Instead, different surfactant concentrations were trialed during emulsion preparation but again the resulting polyHIPEs were punctuated by several unusually large craters amongst a population of smaller voids as shown in Figure 1a,b which represent surfactant concentrations of 4.5 %/v and 5.5 %/v, respectively. For example, the average +/\(-\) pore size was 7.391 \(\pm\) 6.727 \(\mu\)m (\(n=30\)) for Figure 1a. Our overarching goal was to demonstrate the use of polyHIPEs for isocratic separations of small molecules. This requires a tighter size distribution of void sizes for improved chromatographic efficiency, as previously reported by [PERSON] [11], [PERSON] _et al._[38] and [PERSON] _et al._[39] who studied the separation efficiency for small retained molecules on commercial polymer monoliths. For this reason, GMA-\(co\)-EDMA polyHIPEs were rejected as candidates for further study, but not before also investigating the possibility of forming the polyHIPEs within a PEEK column housing (albeit with non-optimum pore morphology). To this end, a comparison was made by forming a GMA-\(co\)-EDMA polyHIPPE within unmodified PEEK (Figure 1c) and within PEEK that was surface modified with glycidyl methacrylate (Figure 1d). Unsurprisingly, large sections of the monolith within the unmodified tubing were easily pushed out by a modest flow of solvent but this was also the case for the modified tubing; in both cases, a large wall void is clearly seen and the remaining polyHIPE appeared to have shrunken in size within its mould. It is interesting to note that no other reports appear in the literature in which the work of [PERSON] _et al._[35] has successfully been repeated. However, during the preparation of this manuscript, a report has recently emerged in the literature in which the combination of sodium and vanadium(V) as catalysts during the PEEK sulphonation step significantly increases the yield  
Figure 1: GMA-\(co\)-EDMA polyHIPE with **(a)** 4.5% surfactant; and **(b)** 5.5% surfactant. A GMA-\(co\)-EDMA polyHIPE with 4.5% surfactant was formed in **(c)** unmodified 0.76 mm i.d. PEEK; and **(d)** GMA-modified 0.76 mm i.d. PEEK.