Xerogels stage

Figure 2.3 In the first step, the mixture is emulsified by stirring, and in the second step, an amorphous network of glassy material is prepared at room temperature by the hydrolysis of suitable monomers. The reaction proceeds to a condensation polymerization reaction, followed by subsequent formation of the sol to the gel and xerogel stages. (Adopted from Merck.com)...

Mann S., Bnrkett S.L., Davis S.A., Fowler C.E., Mendelson N.H., Sims S.D., Walsh D., Whilton N.T. Sol-gel synthesis of organized matter. Chem. Mater. 1997 9 2300-2310 Matsni K., Matsuzuka T., Fujita H. Fluorescence spectra of 7-azaindole in the sol-gel-xerogel stages of silica. J. Phys. Chem. 1989 93 4991 994... 

Stable hydrogen bonds of the type=Si-0 H0-Si=play an important role in formation of the hydrogel structnre [8, 9], The preparation of a methylsilicic acid hydrogel is an intermediate stage of polymethylsiloxane synthesis, the final solid product of which is a xerogel of methylsilicic acid obtained from hydrogel by its desolvatation (dehydration) at 120°C according to Eq. (21.1) ... 

As a result, stage I directs the overall porosity of xerogel emin < e < emax), stage II determines the pore volume - size distribution, and stage III includes the decrease of surface area (the main factors here are pH, temperature and remaining liquid content). 

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