Porous monoliths

Svec, F Frechet, JMJ, Molded Rigid Monolithic Porous Polymers An Inexpensive, Efficient, and Versatile Alternative to Beads for the Design of Materials for Numerous Applications, Industrial and Engineering Chemistry Research 38, 34, 1999. 

Plate type packing to separate the phases is discussed by Carlsson et al. (1983) and by Hatziantoniu etal. (1986). De Vos et al. (1982,1986) describe use of a monolithic porous catalyst with vertical and horizontal channels. The liquid phase flows downward through an array of parallel channels in the monolith, while gas moves in cross flow through a separate set of channels. Another approach treats the catalyst to make part of the surface hydrophobic or lyophobic (Berruti et aL, 1984). The gas phase has direct access to the surface on these unwetted portions of the surface, resulting in partial, spatial segregation of the phases. 

Yu, C., Davey, M. H., Svec, F, and Frechet, J. M. (2001). Monolithic porous polymer for on-chip solid-phase extraction and preconcentration prepared by photoinitiated in situ polymerization within a microfluidic device. Anal. Chem. 73, 5088-5096. 

Cooper, A. I. Holmes, A. B. Synthesis of Molded Monolithic Porous Polymers Using Supercritical Carbon Dioxide as the Porogenic Solvent. Adv. Mater. 1999, 11, 1270. 

Microfluidics and miniaturization hold great promise in terms of sample throughput advantages [100]. Miniaturization of analytical processes into microchip platforms designed for micro total analytical systems (/i-TASs) is a new and rapidly developing field. For SPE, Yu et al. [123] developed a microfabricated analytical microchip device that uses a porous monolith sorbent with two different surface chemistries. The monolithic porous polymer was prepared by in situ photoinitiated polymerization within the channels of the microfluidic device and used for on-chip SPE. The sorbent was prepared to have both hydrophobic and ionizable surface chemistries. Use of the device for sorption and desorption of various analytes was demonstrated [123]. 

Figure 25.3 (a) Photograph of monolithic porous carbon, (b) SEM image of porous carbon, (c)... 

Fig. 6.20. Schematics for the preparation of monolithic capillary columns. First, the bare capillary is filled with the polymerization mixture (step a) that contains functional monomer, crosslinking monomer, initiator, and porogenic solvent. Polymerization (step b) is then initiated thermally or by UV irradiation to afford a rigid monolithic porous polymer. The resulting monolith within the capillary is washed (step c) with the mobile phase using a pump or electroosmotic flow and used as for the CEC separations.

When used as monolithic, porous catalytic membranes, the platinum group metals provide higher mechanical stability and heat conductivity than conventional supported metal catalysts. The cost, however, can be an issue. An economically feasible solution to... 

Hydrophilic polystyrene-based continuous beds bearing a hydrophilic surface on a hydrophobic polymeric support were prepared by a two-step modification of polychloromethylstyrene monolith first with ethylenediamine followed either by a reaction with y-gluconolactone or with chloroacetic acid [57,122]. Activation could also be performed by grafting 4-vinyl-2,2-dimethylazactone onto the monolith porous surface [123]. 

Different photocatalytic reactor configurations are reported in the literature including annular reactor with a small thin film of catalyst coated on the iimer surface of the outer annulus, flat-plate fluidized beds, annular packed beds, and catalyst coated on honeycombed monoliths, porous fibrous mesh, and optical fiber bundles (31,32). 

Dulay, M.T., et al.. Preparation and characterization of monolithic porous capillary columns loaded with chromatographic particles. Anal. Chem., 70, 5103,1998. 

The monolithic porous structure has also the same properties and suitable for the reaction solid phase. However, it is difficult to remove the monolith from the chip after an assay so the chip is then disposed. Hence, this happens even though the change of the beads is very easy. Therefore, the monolithic format is not favorable unless the cost of the chip is very low. 

Svec, F. Frechet, J.M.J. Molded rigid monolithic porous polymers an inexpensive, efficient, and versatile alternative to beads for the design of materials for numerous applications. Ind. Eng. Chem. Res. 1999, 38, 34-48. 

Wang Z, Li F, Eigang NS, Stein A (2006) Effects of hierarchical architecture on electronic and mechanical properties of nanocast monolithic porous carbons and carbon—carbon nanocomposites. Chem Mater 18 5543-5553... 

Obtained from the thermal pyrolysis ( 1000 °C) of selected polymers and may be monolithic, porous or reticulated. Produced from a variety of starting materials such as petroleum or naturally occurring cokes and yield bulk structures of varying grain size, crystallite orientation, purity, porosity, strength, and particle size. 

Bakry, R., Bonn, G. K., Mair, D., and Svec, F. 2007. Monolithic porous polymer layer for the separation of peptides and proteins using thin-layer chromatography coupled with MALDI-TOF-MS, Anal. Chem., 79 486 93. 

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