# Methacrylate Polymer Monoliths for Separation Applications
## 4 Conclusions and Outlook  
This review paper serves to give the reader an overview of some important developments over the last 20 years in the preparation and application of methacrylate monoliths for separation and purification of chemical and biological species. This particular branch of polymer monolith has received more research and development attention, as well as applications than other types of polymer and non-polymer based monoliths. This can be seen to be due to the advantages of methacrylate-based monoliths. They can be prepared via a number of synthetic routes, and be functionalized with a wide variety of chemical (ion exchange groups, alkyl chains, ethers, diols, OH groups), as well as biological functional groups such as proteins and other bio-affinity ligands. Therefore tailoring their chemical interactions is possible and has been achieved for a wide variety of application as noted in this review. The ease of functionalization and preparation of methacrylate monoliths has been a key factor in their appeal to researchers, however it must be stressed that this work is still very much in the early stages and significant scope remains for improvement of existing chemical modifications in terms of control and in the discovery of new chemical transformations and polymerization control mechanisms. Of more importance and which ultimately will have a greater impact on the success of methacrylate monoliths is a greater understanding of effects of the physical architecture of the monolith on the chromatographic separation or amplification of analytes. An understanding of the physical architecture would involve fully understanding the complex interplay of flow, mass transfer, tortuosity, monolith dimensions, diffusion processes, porosity and pore size distribution, as well as network homogeneity and relating all of these to the subsequent separation and to the fabrication method employed in each case. Some steps have been taken in this direction but more work needs to be done. It can be seen that methacrylate based monolithic stationary phases have been examined in detail for both chemical and biological separations. This development has overcome some perceived shortcomings and led to valuable commercial outputs, such as CIM(tm), as well as the development of methods which have been validated for current Good Manufacturing Practice (cGMP) in the pharmaceutical and other industrial sectors by many research groups [140; 146]. In particular, methacrylate have been shown to be adept in the separation and amplification of biological species and in some cases have significant potential for industrial applications. The possibility of scaling up production of monoliths to multi-liter volumes has also been investigated [146; 166]. The suitability of methylates for the separation of small molecules is still a matter of debate, but some examples of separations involving alkylbenzenes, herbicides and pharmaceuticals have been reported. Innovative fabrication methods, such as e-beam curing, and 3D printing, have been utilized alongside more tried and tested polymerization reactions. One other attractive feature of methacrylate based monolithic media comes from the fact that application areas are varied ranging from detection of herbicides, pharmaceuticals, pesticides, and acidic and basic molecules to proteins, peptides, amino acids and DNA in various forms. A key factor in this area of improvement is a better understanding of the structure of the monoliths. Commonly used techniques such as SEM and TEM should be increasingly complemented by other sectioning and computer reconstruction of the scanned layers to produce a 3D digital topographic reconstruction of the porous structure [82; 165]. However, correct interpretation of the data is crucial. This characterization technique in conjunction with advances in 3D printing could lead to reproducible production of well-defined macroporous and microporous structures.