LAUSR

Abstract The soft-templating method is important in the preparation of ordered mesoporous carbon materials. In the process, careful removal of the block template is a critical step in obtaining a highly ordered mesostructure before carbonization. In this study, the dynamic structure evolution of template removal by means of calcination using both high (3 °C/min) and low (1 °C/min) heating rates was monitored using an in situ GISAXS technique. The real-time d-spacing and order degree parameters including the mesochannel dislocation and grain size of the ordered structure were determined as a function of calcination time. The results showed that the entire structure evolution process could be divided into three stages according to variable rates of d-spacing: glass transition stage, molten phase transition stage, and pyrolysis stage. In the first stage, thermal expansion transition into template shrinkage was observed as the polymer chain transitioned from a rigid to a softer state. Shrinkage of the template occurred, while a highly ordered mesostructured remained. In the second stage, the template became flexible after the molten phase transition, and the rate of structure change gradually increased, accompanied by mesochannel dislocation. Fast pyrolysis occurred in the last stage, the ordered structure was destroyed, and internal stress was released. This phenomenon was also clearly observed when the heating rate was 3 °C/min. The final ratio of dislocation comparing the state before and after template removal was 9.13, which is significantly higher than the value of 5.84 observed with a heating rate of 1 °C/min. The results indicated that the ordered mesostructure after template removal was determined by not only the critical temperature but also the heating profile during the entire process of structure evolution. A hypothetical mechanism is proposed to explain the structure evolution of template removal for ordered mesoporous films prepared by a soft-templating method. A reasonable design for a heating profile for template removal based on this in situ GISAXS study can be an effective method for improving the quality of mesoporous films.