Molecular design of polymer precursors for controlling microstructure of organic and carbon aerogels

Organic and carbon aerogels were prepared by sol–gel polymerization of phenol, melamine and formaldehyde, followed by supercritical drying and pyrolysis. The effect of the mole ratio of melamine/phenol (M/P) on microstructure of organic and carbon aerogels was investigated by N2 adsorption, SEM and TEM. Coordination M/P could change the hydrophilicity and cross-linking density of polymer framework, thereby affecting polymer colloid nanoparticle nucleation and growth, and ultimately determine the 3-dimensional network of the gels. The bulk densities of organic and carbon aerogels have maxima at M/P of 0.1, which are inversely proportional to volume shrinkage of gels during drying and pyrolysis. The size of the nanoparticles could be adjusted by varying M/P in the range from 10 to 22 nm. The mesopore volumes of organic and carbon aerogels are tailored in the range of 1.4–2.9 and 0.8–2.5 cm3/g, respectively. The average mesopore diameter has experienced a decreasing first and increasing afterward tendency with the increase of M/P, and exhibit a minimum at M/P of 0.1.