3.1. Self-assembly mechanism
The process of samples preparation can be briefly summarized as follows. Organic–organic composite sol (i.e. resorcinol/formaldehyde and Brij58 in basic ethanol at room temperature) is firstly synthesized, and then dip-coating technology is used to prepare organic composite thin film on the substrate, and finally ordered mesoporous carbon thin film was formed after heat treatment and carbonization. Many experiments show that the aging time of sol and heat treatment after dip-coating have remarkable effects for the periodicity of thin film. In addition, we find that the coating technique of the film has also obvious effects for the periodicity of film. Fig. 1 schematically illustrates the procedure of ordered mesoporous carbon thin film fabrication. The synthesis process of mesoporous carbon thin film involves four basic steps: (1) RF-Brij58 film casting, (2) structure refining through solvent evaporation, (3) thermopolymerization of the carbon precursor, and (4) carbonization. Solvent evaporation and thermopolymerization exist together at 100 °C, both of them are followed by self-assembly. But the key question is that which kind of self-assembly plays a leading role on the mesoporous structure formation of the film. Recently, Bein et al. present a new mechanism for mesostructure formation of ordered mesoporous carbons (OMCs) with SAXS and GISAXS measurements. They consider the structure formation in OMCs systems does not occur during the evaporation process but during the thermopolymerization step, which is called thermally induced self-assembly (TISA) [30].