## 5 Chemistry of Polymer Rods
### Surface Grafting
[PERSON] _et al._[90] prepared a polyethyleneimine (PEI) modified ion-exchanger based on poly(methyl methacrylate-co-EGDMA) monoliths. The presence of PEI provided better permeability for the separation of bovine serum albumin (BSA). The binding capacity of the monolithic support was enhanced by increasing the molecular weight of PEI, indicating that the brush ligand derived from the surface captured more protein by multiple binding sites. DEAE-dextran has been employed by [PERSON] _et al._[91] to prepare anion-exchange monolithic columns for the separation of proteins. The monolithic column modified with this polymer exhibited an even lower pressure drop and a relative higher binding capacity, which constitute an important potential for a rapid analysis and separation of proteins. Regarding the preparation of hydrophobic interaction chromatography (HIC) stationary phase for the separation of proteins, the hydrophobicity of separation media can be generally adjusted by selecting the types of ligands. Poly(_N_-isopropylacrylamide) (polyNIPAm) was used as ligand to modify a polymer monolith and the modified product undergo an expected change in hydrophobicity by varying the temperature and/or salt concentration in the process of chromatographic separation. PolyNIPAm is one of most widely studied thermosensitive polymers with low critical solution temperature. This means that the polymers can be subjected to a reversible alteration in their hydrophobic/hydrophilic behavior due to the conformation transition of polyNIPAm chains [92, 93]. [PERSON] _et al._[94] developed a kind of thermal-responsive material. A composite that changes its permeability with temperature leading to the possibility of a thermal gate, a thermal valve, or a thermal control of hydrophobicity/hydrophilicity was reported. A method to modify the internal pore surface of rigid polymer monoliths by grafting-on polyNIPAm is also described. Thus, isocratic HIC of proteins was reported. This constitutes a novel separation technique based on changes in surface polarity (and thus adsorption) accompanying the temperature-induced phase transition of the grafted polyNIPAm. More recently, [PERSON] _et al._[95] prepared a grafted-polyNIPAm monolith with a controlled amount of polymer ligands. The hydrophobicity of the ligands could be controlled by changing the salt concentration in the chromatographic separation, and sodium sulfate showed the best ability. This monolith enlarged the types of separation media for HIC of proteins, extending this concept. Photo-grafting can be used for a fast, efficient and versatile surface functionalization. [PERSON] _et al._[96, 97] showed that the use of simple photo-masks precisely positioned atop of the monolith enables the grafting for proceeding strictly in those confined areas of the monolith exposed to radiation, while no functionalization is observed in dark areas. The photo-grafting of porous three-dimensional materials has been achieved using a benzophenone-initiated surface photo-polymerization within the pores of a macroporous polymer monolith contained in a fused silica capillary. [PERSON] _et al._[3, 7] and [PERSON] and coworkers [98] also reported the successful use of the 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) radical, reversibly trapped during the mold polymerization for grafting the pore surface with functional vinyl monomers _in situ_ to easily control the pore surface chemistry. [PERSON] _et al._ introduced a method for grafting methacrylic acid (MAA) onto the internal surface of hydrolyzed poly(glycolylethylacrylate-co-EGDMA) monoliths with potassium peroxydisulfate in an _in situ_ polymerization. The resulting polymer chains showed a pH-responsive monolithic stationary phase used for the fast purification of the Lys from chicken egg white (CEW) [99]. On the other hand, several advantages can be reached when ROMP-based route is used. Functionalized continuous rods were synthesized by one additional synthetic step that takes advantage of the living character of the ROMP-based copolymerization [100].