Toward optimization of macroporous silica gels for application to capillary or microchip-based CEC and LC

Silica aerogels were prepared via the sol-gel process using tetramethoxysilane (TMOS) as the precursor and polyethylene oxide (PEO) of molecular weights 10,000 and 100,000 to provide a polymeric template for gelation. The experiments included eleven different formulations ranging from 100% 10,000 MW PEO to 100% 100,000 MW PEO in 10% increments. The total concentration of PEO was kept constant throughout the experiment. The gelation time of the wet-gel prepared using 10,000 MW PEO was 15.3 (+/- 0.1) x 10(3) s, while gelation occurred almost 30 times faster by using long-chain 100,000 MW PEO. The surface area of aerogels prepared with 10,000 MW PEO was 40 m(2)g(-1) and that of 100,000 MW PEO aerogels was more than an order of magnitude larger. The Young's modulus of 10,000 MW PEO aerogels was 1.2 (+/- 0.3) MPa while that for 100,000 MW PEO aerogels was almost four times larger. Estimated pore sizes for all types of gels were in the macroporous region. The estimated pore sizes for 10,000 MW PEO were an order of magnitude greater than those estimated for 100,000 MW PEO. The physical properties of silica aerogels such as gelation time, pore size, surface area, and Young's modulus can be tailored to make them suitable for application as separation media in HPLC and CEC. (C) 2004 Elsevier B.V. All rights reserved.