## 5 Chemistry of Polymer Rods  
According to the application of the polymer support obtained, a specific chemical functionality in the structure of the polymer rod will be required. For example, continuous polymers formed from hydrophobic monomers can be used as stationary phase in reversed phase chromatography (RPC); those from ionic group-containing monomers could be used in ion exchange chromatography (IEC) or  
Figure 4: Effect of flow velocity on back pressure in the molded poly(glycolyl methacrylate-co-ethylene dimethacrylate) and poly(styrene-co-divinylbenzene) 100 mm \(\times\) 8 mm monoliths. Conditions: mobile-phase tetrahydrofuran. (a, top) Polymerization mixture: glycolyl methacrylate 24%, ethylene dimethacrylate 16%, cyclohexanol and dodecanol contents in mixtures 54 + 6%, respectively; temperature 80 \({}^{\circ}\)C (1); 54 + 6, 70 \({}^{\circ}\)C (2); 54 + 6, 55 \({}^{\circ}\)C (3); 57 + 3, 55 \({}^{\circ}\)C (4), and 45 + 15%, 70 \({}^{\circ}\)C (5). (b, bottom) Polymerization mixture: styrene 20%, divinylbenzene 20%, dodecanol and toluene contents in mixtures 40 + 20%, respectively; temperature 80 \({}^{\circ}\)C (1); 40 + 20, 70 \({}^{\circ}\)C (2); 45 + 15, 80 \({}^{\circ}\)C (3); 45 + 15, 60 \({}^{\circ}\)C (4); 50 + 10, 70 \({}^{\circ}\)C (5) and 60 + 0%, 70 \({}^{\circ}\)C (6). From [3], reprinted with permission from the American Chemical Society.  
as carriers in capillary electro-chromatopography (CEC); and those from chiral units are required for enantioselective chromatographic separations.  
As the polymerization mixture consists of a single phase, the possible combination of monomers used in the preparation of continuous polymers is higher than that in the case of suspension polymerization reactions. For this reason, a greater diversity of surface chemical structures could be obtained. Nevertheless, the reaction conditions optimized for a specific system cannot be transferred directly to another system. The reaction conditions for each special system must be optimized. Figure 5 shows different monomers and cross-linking agents used for continuous macroporous polymer synthesis. Hydrophobic monomers such as Sty (**1**) and butylmethacrylate (BMA) (**4**), monomers with reactive functional groups such as the GMA (**5**), chloromethylstyrene (CMS) (**2**) and 2-vinyl-4, 4-dimethylazolactone (VAZ) (**7**), monomers with protected functionality such as 4-acetoxystyrene (**3**), water soluble hydrophilic monomers such as AAm (**8**), acid 2-acrylamide-2-methyl-1-propanesulfonic acid (**6**) and zwitterionic monomer such as _N,N_-dimethyl-_N_-methacryloyloxyethyl-_N_-(3-sulphopropyl ester) ammonium betaine (**9**) were found. The cross-linking agents commonly used are DVB (**10**), BIS (**11**), EgDMA (**12**) and TRIM (**13**).  
Figure 5: Monovinylic monomers and cross-linkers used in the preparation of porous polymer rods.  
For several applications, as in the case of affinity chromatography in porous media, the covalent binding of a ligand onto the polymeric material is necessary. The surface functionalization and chemistry and porous properties of the monoliths can be tailored to suit a variety of applications by adjusting the composition of the initial monomer solution and the polymerization conditions [57].  
However, on the basis of previous works, the design of successful functionalized monoliths has followed three main strategies: (1) incorporation of monomers that provide functionalities and/or perform post-chemical reactions (activation, modification, _etc._) on the functional groups of the monolith yielded for the coupling or immobilization of a specific ligand; (2) surface grafting which could greatly increase the number of active sites of the support; and (3) synthesis by Molecularly Imprinted Monoliths (MIP) technique.