Poly(ethylene glycol) as structure directing agent in sol-gel synthesis of amorphous silica

Porous amorphous silica obtained by the sot-gel method with poly(ethylene glycol) (PEG) as structure directing agent is investigated. In this paper, we use the PEG with molecular weight 400, 1300, 3000, 6000, 20,000, 100,000, 200,000 and vary the concentration of the polymer solution in a wide range. The analysis of nitrogen adsorption-desorption data and transmission electron microscopy shows that depending on the combination of molecular weight and concentration of the PEG solution the microporous and mesoporous silica materials can be obtained. It was determined that using the solution of PEG-400, 1300 independently of the concentration the mesoporous silica is formed. When the diluted and concentrated solutions of PEG-3000, 6000, 20,000, 100,000, 200,000 are used it produces also the mesoporous materials. In the field of transitional concentrations of PEG the microporous silica with fraction of micropores equals 95% is generated. Revealed regularities are generalized and shown on the texture diagram. (C) 2014 Elsevier Inc. All rights reserved.