Control of the Porous Properties

Closely connected with control of the flow properties of Slurries is control of their density. For a given compn considerable variation in Slurry d can be achieved by introduction of small amounts of porous solids by air entrapment (aeration) and by inclusion of small amounts of gas producing ingredients. It is the latter approach (ie, gas-formers) that is... 

We also tried an immobilization of crown ether on the surface of a porous support since it is preferable from an economic standpoint as well as the ease of the control of the physical properties of the beads. In the actual application of the crown polymers for the separation of some salts by the column method, they have to be processed... 

We have found that in the system of presulfate initiator, the PVAc latexes are not dissolved transparently in the methanol-water mixture [8], and in the system of HPO initiator, the extraction of the polymer from the PVAc latex films with acetone greatly depends on the polymerization condition [9]. These results suggest that if a polymerization method can be found in which the grafting polymerization of VAc onto PVA is controlled to the minimum, a large portion of PVAc in the latex film will have a chance of extraction with solvents. In this Chapter, the preparations of the unique porous films from the PVAc latexes containing PVA as a protective colloid by an extraction of the PVAc particles with acetone and the characteristic properties of the porous films are summarized. 

This technology was extended to the preparation of chiral capillary columns [ 138 -141 ]. For example, enantioselective columns were prepared using a simple copolymerization of mixtures of O-[2-(methacryloyloxy)ethylcarbamoyl]-10,11-dihydro quinidine, ethylene dimethacrylate, and 2-hydroxyethyl methacrylate in the presence of mixture of cyclohexanol and 1-dodecanol as porogenic solvents. The porous properties of the monolithic columns can easily be controlled through changes in the composition of this binary solvent. Very high column efficiencies of 250,000 plates/m and good selectivities were achieved for the separations of numerous enantiomers [140]. 

The ability to achieve precise and independent control over both the porous properties as well as the level of charged moieties of the rigid monolithic stationary phases opened new avenues for studies focusing on the effects these properties exert on the... 

In addition to utilization of monoliths as a column material, two reports describing respectively silicate and synthetic organic polymer based monolithic frits were published recently [85,86], The conventional method of frit fabrication for a particle packed column usually involves thermal sintering of a section of the packing material, such as bare or octadecyl silica, using a heating device. This approach has several weaknesses such as the lack of control of the temperature and porous properties of the frit that decreases reproducibly of the fabrication process. 

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