Chemical interactions of surface-active agents with growing resorcinol-formaldehyde gels.

The influence of cationic, anionic, and nonionic surfactants (S) on the characteristics of carbon xerogels was analyzed. The polymerization of resorcinol (R) and formaldehyde (F) was developed in an aqueous solution of S without any additional catalyst. The gels obtained were dried in air to obtain organic xerogels and then carbonized to carbon xerogels. The prepared samples were characterized by FTIR, TG, SEM, and N(2) and CO(2) adsorption. The formation of RF-S copolymers was observed for cationic and nonionic surfactants, but this was not observed for anionic S, probably because of repulsive electrostatic interactions between the two organic phases. Nevertheless, anionic S leads to a greater morphological transformation with the formation of nonporous needle particles associated with the higher pH induced by this S. Carbon xerogels are microporous materials with interesting molecular sieve behavior. The RF-S composites undergo greater shrinkage than do the pure RF xerogel; consequently, a narrower microporosity is obtained.