Organically modified silica preparation

Fig. 1 Chemical structures of the polymers commonly used for preparation of beads poly (styrene-co-maleic acid) (=PS-MA) poly(methyl methacrylate-co-methacrylic acid) (=PMMA-MA) poly(acrylonitrile-co-acrylic acid) (=PAN-AA) polyvinylchloride (=PVC) polysulfone (=PSulf) ethylcellulose (=EC) cellulose acetate (=CAc) polyacrylamide (=PAAm) poly(sty-rene-Wocfc-vinylpyrrolidone) (=PS-PVP) and Organically modified silica (=Ormosil). PS-MA is commercially available as an anhydride and negative charges on the bead surface are generated during preparation of the beads...

Figure 8 Preparation of organically modified silicas via sol-gel methodology...

Sol-gel techniques were used to prepare porous, organically modified silica materials. The introduction of organic groupings was carried out with alkoxysilanes as precursors methyl and propyl amino groups were used. The results show that high-porosity materials can be synthesized the microstructure strongly depends on reaction conditions such as composition, solvent, catalyst type, and concentration. Microstructure tailoring affects mechanical as well as adsorption properties, and custom-made materials such as abrasives and adsorbents with special properties were synthesized. 

Summary Mixed functionalized octa( -alkyl/halogenalkylsilsesquioxanes) with different side chains has been prepared by acid-catalyzed cohydrolysis of w-alkyl- and lialogenalkyltrichlorosilanes. The silsesquioxane mixtures were separated in preparative amounts with normal-phase HPLC. Mixed functionalized octa( -alkyl/halogenalkylsil-sesquioxanes) with different side chains are suitable examples of an organically modified silica gel. They can be modified by nucleophilic substitution of the halogen atom with -PPh and rhodium-phosphino complexes are be formed. 

Dagan, G., S. Sampath, and O. Lev, Preparation and utilization of organically modified silica-titania photocatalysts for decontamination of aquatic environments,... 

Oh E., Chakrabarti K., Jung H., Whang C. Microstructures and mechanical properties of organically modified silicate prepared under various process conditions. Mater. Sd. Eng. 2002 B90 60-66 Pope E.J.A., Asami M., Mackenzie J.D. Transparent silica gel-PMMA composites. J. Mater. Res. 

Low temperature sol-gel technology is promising approach for preparation of modified with organic molecules silica (SG) thin films. Such films are perspective as sensitive elements of optical sensors. Incorporation of polyelectrolytes into SG sol gives the possibility to obtain composite films with ion-exchange properties. The addition of non-ionic surfactants as template agents into SG sol results formation of ordered mechanically stable materials with tunable pore size. 

Flash chromatography is widely employed for the purification of crude products obtained by synthesis at a research laboratory scale (several grams) or isolated as extracts from natural products or fermentations. The solid support is based on silica gel, and the mobile phase is usually a mixture of a hydrocarbon, such as hexane or heptane, with an organic modifier, e.g. ethyl acetate, driven by low pressure air. (Recently the comparison of flash chromatography with countercurrent chromatography (CCC), a technique particularly adapted to preparative purposes, has been studied for the separation of nonchiral compounds [90].)... 

---