Organically monoliths

Since 1992, a vast variety of rigid organic monolithic stationary phases with different chanistry, functionality, and column geometry has been reported for HPLC as well as CEC applications, as summarized by the number of excellent reviews [25-32,213], The development and enhancanent of monolithic stationary phases is stiU a rapidly growing area of research with scientific and industrial interest. 

Organic monoliths are based on copolymerization of a monofunctional and a bifunctional (uncommonly trifunctional) organic precursor in the presence of a suitable initiator and a porogenic solvent. During the last 15 years, a vast number of different monomers and cross-linkers have been introduced and copolymerized using different polymerization techniques and initiators. A general survey of the tremendous amount of scientific contributions can be gained from numerous reviews [25-32],... 

Free radical copolymerization of a monovinyl compound and a divinyl cross-linker is by far the most commonly employed mode of polymerization for the preparation of organic monoliths. 

Table 1.1 gives a comprehensive, albeit fragmentary, snmmary of investigated organic monolithic polymer systems (based on all different kinds of styrene, acrylate, methacrylate, (meth)acrylam-ide building blocks, as well as mixtnres thereof) together with their preparation conditions and ntilization as stationary phase. 

Summary of Organic Monolithic Polymer Systems That Have Been Introduced in Literature Listed Together with Their Mode of Polymerization, Porogenic Solvent, and Their Key Application in HPLC and CEC Separation... 

General Pore Formation Mechanism of Organic Monoliths... 

Due to the fact that thermally initiated free radical copolymerization is by far the most routinely employed method for fabrication of organic monolithic stationary phases, the pore formation mechanism is discussed for this particular kind of polymerization. 

Due to their defined monomodal macropore distribution (see Section 1.2.1), monolithic stationary phases, based on polymerization of organic precursors, are predestined for efficient and swift separation of macromolecules, like proteins, peptides, or nucleic acids, as their open-pore structure of account for enhanced mass transfer due to convection rather than diffusion. In fact, most of the applications of organic monolith introduced and investigated in literature are directed to analysis of biomolecule chromatography [29]. 

Faure et al. [22] described nanoelectrochromatography on poly (dimethyl)-siloxane microchips using organic monolithic stationary phases for analysis of derivatized catecholamines. Surface modification of the PDMS material was carried out by UV-mediated graft polymerization. The efficiency of the unit was ascertained by measuring theoretical plates, which were 200,000 per meter. Furthermore, the authors optimized the separation by using pinched and electrokinetic modes at different applied potential of l.OkV/cm (Fig. 7.6) and 30kV/cm (Fig. 7.7) for the pinched and electrokinetic... 

During the past 10 years, in addition to silica-based monoliths [12], a broad range of organic polymeric monoliths has been studied. Their most advantageous attribute is their chemical stability over a wide pH range. The most common organic monoliths were the results of methacrylate [13] and styrene [14] monomers. Some examples that confirm the utility of monolithic columns in IPC are described below. 

II photoinitiators and react with the plastic surface through hydrogen abstraction from COC surfaces. It is shown that type I photoinitiators can simultaneously act as type II photoinitiators. The mechanism allows the use of a single initiator to functionalize the COC surfaces and to synthesize the organic monolith simultaneously. The only requirement is to have a polymerizing formulation containing a sufficient photoinitiator concentration. This simple approach is expected to facilitate in the development of organic monolith as a stationary phases inside thermoplastic microchannels. 

Fame K, Bias M, Yassine O, Delaunay N, Cretier G, Albert M, Rocca JL (2007) Electrochromatography in poly(dimethyl)siloxane microchips using organic monolithic stationary phases. Electropliorcsis 28 1668-1673... 

Abstract American Aerogel produces an organic monolithic aerogel panel called Aerocore. Its properties have been optimized for the mass production of vacuum insulation panels (VIPs). This contribution summarizes the history of the company and describes the Company s materials. 

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