Sol–Gel with Phase Separation. Hierarchically Porous Materials Optimized for High-Performance Liquid Chromatography Separations

Abstract

Sol-gel processes for fabricating oxides or metalloxane polymers with controlled porous structures have been reviewed. Gel materials having controlled macropores are synthesized by polymerization-induced phase separation and concurrent sol-gel transition in a variety of chemical compositions. Several variations of tailoring mesopore structures within the macroporous materials are introduced, which enable one to design hierarchically porous metal oxide and metalloxane polymer materials. Applications of monolithic silica gels having hierarchical macro/mesoporous structure to the separation media of high-performance liquid chromatography, HPLC, are described.

Hierarchical Porosity in Silica Thin Films by a One-Step Templating Strategy Using a Stimuli-Responsive Bioderived Glycolipid

“…46 If some key elements found in chemical cooling are lacking from this study, such as polymers and/or additional solvent (besides water and ethanol), this mechanism was reported for other systems composed of SiO2/CTAB. 47 Whether this mechanism applies or not to the system studied here, it cannot be excluded, even if it is still uncertain for the following reasons: 1/ Chemical cooling has been largely described for the formation of monoliths, where evaporation of the solvent is slow, which is not the case for fast-evaporating systems composed of silica thin films; 2/ a large literature exists on the synthesis of porous silica thin-films (some examples given in Table 1) an inverse proportionality between the amount of non-volatile organic compound (e.g., PEO, CTAB) and macropore size 47,48 and a direct one between the amount of solvent and macropore size. 46 This is not the case for our system, where the macropore size increases from sample S1 to S7, that is, with the amount of sophorolipid in solution (Table 3).…”

Core–Shell, Ultrasmall Particles, Monoliths, and Other Support Materials in High-Performance Liquid Chromatography

“…Alkoxysilanes such as TMOS or tetraethoxysilane (TEOS) undergo hydrolytic polymerization accompanied by phase separation in aqueous acetic acid in the presence of polyethylene glycol (PEG) to form monolithic silica having bicontinuous network structures 106 . The amount of PEG in the feed controls phase separation during polymerization 107 .…”

Methacrylate-ester-based Reversed Phase Monolithic Columns for High Speed Separation Prepared by Low Temperature UV Photo-polymerization

“…modification of silica monolithic columns have been extensively One of the recent solutions for high speed separation is the studied, and their users are increasingly widespread. [19][20][21][22] On the ultrahigh pressure liquid chromatography (UPLC). 5,6 In the other hand, polymer-based monolithic columns have unique UPLC, a column packed with micro particles less than 3 μm in advantages such as an availability over a wide pH range and size is used, since the column efficiency increases with simplicity of preparation.…”