| 초록 |
The current fabrication processes of porous materials have unsolved limitations such as limited pore alignment and difficulty in controlling tortuosity. Recently, novel aligned porous materials can be produced by directional freezing, which is a simple and effective method. However, in general, porous polymers prepared by freeze drying are too weak, mainly because of cracking induced by freezing and desiccation stresses. In here, by understanding the freezing process in depth, we dramatically suppressed cracking in final porous polymer membranes. We could make large-area PVDF membranes with through-thickness pores (typically 50~200 µm thickness and 5~10 µm pore size analyzed by SEM) by manipulating freezing front formation in the directional freezing process. The first freezing front formed in directional freezing was related with the nucleation and growth of pure solvent crystals, and the second one was related with the freezing of polymer-rich phases. |
