Silica gels polymer shapes

Solid supports for RP-HPLC are, in most cases, silica gel derivatized with cyano, C4, C8, Q8, or diphenyl groups and, therefore, have limited stability at pH values <2.0 or >8.0. Less commonly used supports are polymer based that will withstand high pH. Besides their carbon load, silica gel particles can be of different sizes, shapes, and with pore sizes ranging from 80 to 500 A. Literally hundreds of different columns are available.147 48 A commonly used particle is spherical, 5 pm in diameter, and with 300-A pore size. Whereas C4 and C8 columns are preferred for proteins or very hydrophobic peptides, C18 is most commonly used for a wide variety of peptides. 

Photopolymerization 0,5 g silica II vras mixed with 2 ml of the liquid monomer or its solution in ethanol in a flat shaped weighing tottle (35 x 30, 15 ml). The photopolymerization was performed in the presence of air by irradiating the mixture for a certain time (3 minutes in a typical experiment) with a high pressure mercury lamp (TQ 105, Heraeus) at a distance of 5 cm without agitation at room temperature. The solid material III (with silica gel shape) was collected quantitatively by filtration, washed with 100 ml ethanol on the filter crucible and dried overnight in vacuo. The weight increase of the sample corresponds well with the polymer formation on the materials III calculated from the results of the elemental analysis. (All experiments were performed twice to control the experimental error.)... 

The major advantage for the usage of LCPs as stationary phases for LC applications is that coating of the polymer on the silica gel is a simple process. However, also comb-shaped polymers prepared by octadecyl-acrylate and 3-mercaptopropyltrimethoxysilane as chain transfer agent can be immobilized on silica gel by bonding. It was shown that the telomer behaves as nematic material in the range of 42-47°C. The separation of geometrical isomers could be achieved. ... 

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