Self-formation of 3D interconnected macroporous carbon xerogels derived from polybenzoxazine by selective solvent during the sol–gel process

Polybenzoxazine (PBZ)-based carbon xerogel has been synthesized by a sol–gel process and carbonization. By different solvents, the microstructure of the porous carbon can be tailored for a wide range of desired properties. In addition, a new aspect to produce 3D interconnected macroporous carbon xerogels by selective solvent via self-formation is introduced. Dimethylformamide (DMF), dioxane, and isopropanol are separately used as a solvent during a sol–gel process. The SEM micrographs reveal different structures of carbon xerogel depending on the type of solvent used. Using DMF as a solvent during a sol–gel process and ambient pressure drying, the carbon xerogel shows a similar porous structure to that of a PBZ-based carbon aerogel obtained through supercritical CO₂ drying. In the DMF system, a short gelation time is observed (1.15–3 h) due to the fast ring-opening polymerization accelerated by DMF resulting in the formation of 3D interconnected macroporous structure without using any template. Comparing the rates of cluster growth between DMF and dioxane systems, the rate of cluster growth in dioxane system is slower than that of DMF system, implying good miscibility between PBZ and dioxane. Moreover, microporous spherical particles are obtained from the isopropanol system due to the self-micelle-like formation.