Organic xerogels based on condensation of different m-substituted phenols with formaldehyde

Four samples of organic xerogels have been prepared by polycondensation of different m-substituted phenols (3-aminophenol, m-cresol, phenol and resorcinol) with formaldehyde and subsequent drying. From the set of tested solvents, n-butanol has been chosen as the most suitable one. The reactivity of the m-substituted phenols was ascertained in the order phenol < m-cresol < resorcinol < 3-aminophenol. Phenol and m-cresol did not completely react with formaldehyde during polycondensation reactions. The used type of m-substituted phenol strongly influenced the properties of the final material (the appearance of the organic xerogels, the values of densities and shrinkage after drying, the amount of humidity released during drying and the carbon yield after pyrolysis). The pyrolytic process has been evaluated by TG-MS as three-step process. The first step was characterised as volatile substances loss (n-butanol and water) and mostly CO2 evolution, the second step as evolution of the rest volatiles and the beginning of the carbonisation processes, whilst during the third step merely carbonisation reactions occurred. On the basis of all considered results, 3-aminophenol has been evaluated as the most appropriate precursor for carbon xerogel preparation. It is cheap and the most reactive; it exhibited the lowest values of density, shrinkage and humidity content as well as relatively high carbon yield.