Monolithic stationary phases acrylamide

Hjerten et al. [124] introduced the monolithic stationary phases based on acrylamides in the late 1980s. The cross-linked polyacrylamide can be directly synthesized within the mold by a one step free-radical chain polymerization. Acrylamide, methacrylamide, or piperazine diacrylamide are often employed as monomers, while V,A -methylene-bis-acrylamide is used as a cross-linker. 2-acrylamido-2-methylpropane sulphonic acid, vinylsulphonic acid, butyl methacrylate, or stearoyl methacrylate are usually added to the polymerization mixture to provide charge and functional groups [114]. 

Hoegger, D.Freitag, R. (2001). Acrylamide-based monoliths as robust stationary phases for capillary electrochromatography. J. Chromatogr. A 914, 211-222. 

More recently, columns have been developed where the stationary phase is formed of a porous polymer network inside the capillary. These are called monolithic phases, and have emerged as an alternative to traditional packed bed columns for use in micro-HPLC. They hold many advantages over traditional packed bed columns, being easy to manufacture since the monolith is formed in situ, often via a one-step reaction process, and its properties such as porosity, surface area, and functionality can be tailored. Another major advantage is that they eliminate the need for retaining frits. These columns can be manufactured from a variety of materials, but the most common include sol-gel, methacrylate-based, acrylamide-based, and styrene-based polymeric structures. 

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