Synthesis and characterization of polybenzoxazine-based carbon xerogels

Abstract

In this present work, the porous carbon, called carbon xerogels, derived from polybenzoxazine (PBZ) were prepared via a sol-gel process prior to the carbonization. By using different types of solvents, the cluster growth behaviour of PBZ during the sol-gel process were different due to the differences in solubility parameters between PBZ and solvents, resulting in different porous properties of carbon xerogels. The solvent with low dielectric constant like dioxane provides the slowest rate of cluster growth and also the smallest clusters of PBZ, yielding carbon xerogel with small particles sizes and pore diameter of 40-200 nm after carbonization. This is in part related to the tendency of the oxazine ring-opening in the solvent with large dielectric constant. PBZ-based carbon xerogels obtained through dioxane system were effectively used as a template to control the size of ZSM-5 catalyst into nanoscale (27-70 nm). On the other hand, the Nano sphere and microsphere of carbon xerogels were obtained by using cationic (hexadecyltrimethylammonium bromide) and non-ionic (polyethylene glycol nonylphenyl ether) surfactants, respectively. In addition, high specific surface (518- 899 m2/g) area and extremely high total pore volume (1.34-6.05 cm3/g) of carbon xerogels could be obtained by varying the amounts of silica loading as a hard template. Mesopore diameter of carbon xerogels was also controlled by varying either the concentrations of cationic surfactant or particle sizes of the silica hard template.