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

摘要

Organic and carbon aerogels were prepared by sol-gel polymerization of phenol, melamine and formal_dehyde, 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 N_2 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 cm~3/g, respec_tively. The average mesopore diameter has experienced a decreasing first and increasing afterward ten_dency with the increase of M/P, and exhibit a minimum at M/P of 0.1.