# Methacrylate Polymer Monoliths for Separation Applications
## 2 Methacrylate Polymer Monoliths
### Functionalization Routes and Functional Groups
#### 2.4.1 Epoxy Group Transformations  
As mentioned before, glycolidyl methacrylate, (**2**), is possibly the most useful monomer for when functionalization of a monolith is required. This is due to the presence of an epoxy group, which lends itself to numerous modifications, for example amination, alkylation (for C\({}_{8}\) or C\({}_{18}\) addition), hydrolysis as well as immobilization of various bio-ligands. The latter is important for a monolith, which is to be used in bio-affinity chromatography. It relies on a reaction between the epoxy or hydroxy groups of the monolith and the NH\({}_{2}\) group of the ligand. The ligand could be an antibody, protein or peptide. A scheme showing some of the potential reactions using epoxide chemistry is shown in Figure 5. Hydroxyl groups can be added by using hydroxyl-ethyl methacrylate as a co-polymer unit or by acid hydrolysis of existing epoxy groups, (Figure 5, reaction (d)). A detailed discussion of the preparation and modification of methacrylate monoliths by these routes has previously been presented by [PERSON] and [PERSON] [9] and more recently by [PERSON] and [PERSON] [7].  
Anion exchange can be facilitated via the polymerization of diethyl amino ethyl methacrylate and (acryloloxy) ethyl trimethyl ammonium chloride [44] (which yields a mixture of strong and weak anion exchange groups), and alternatively glycidyl methacrylate and poly ethylene glycol diacrylate can be photo-polymerized and then modified with diethylamino ethyl (DEAE) [86; 87]. Similar reactions are illustrated in Figure 5 (reactions (a) and (e)). [PERSON] _et al._[86] achieved a thirty-fold increase in ion exchange capacity compared with poly styrene-\(\infty\)-divinyl benzene monoliths that were functionalized for ion exchange, while [PERSON] and co-workers [87] reported low flow resistance and reasonable stability of their monoliths over a fourteen day period of use. These examples illustrate the ability to use functionalized monomers in the polymerization step or polymerize standard monomers and then functionalize as desired. The latter method has the advantage of being able to functionalize the surface of the monolith, while the former produces monoliths with functional groups present on the surface and also in the bulk, which may affect the porosity and structural properties of the monolith, particularly if crosslinking or bonding between the functional groups is possible. Methacrylate is somewhat polar, therefore if a methacrylate based monolith is required for a reverse phase separation, treatment of the epoxide groups with an alkyl alcohol will yield the corresponding non-polar alkyl functionality [88] (Figure 5c).  
The epoxide groups can also be used to produce a bio-affinity monolith. The production of bio-affinity monolithic stationary phases involves the introduction of a protein, amino acid or peptide  
Figure 5: Examples of chemical routes to functional groups on polymer monolith surface using the epoxy group as the starting point, (**a**) functionalization with diethyl amine ethyl; (**b**) Alkyl addition via Grignard reaction; (**c**) alkylation; (**d**) hydrolysis; (**e**) sulfonation; (**f**) biofunctionalization, adapted and redrawn from [9].  
moiety to the monolith. Such bio-affinity functional groups can also be introduced via hydroxyl groups on the monolith. A reaction scheme for a modification of a methacrylate monolith with a bio-affinity ligand is shown in Figure 5f, proceeding through the amine group. Cystamine is a common example of a ligand used to modify methacrylate monoliths for bio-affinity and pharmaceutical applications [89].