LAUSR

Abstract A hierarchical flower-like ordered arrangement of the pores in the porous film was explored by combination of the breath figure technique and layer-by-layer solution casting process. A layer-by-layer polymers system of polystyrene (PS) and polyimide (PI) was used to form uniform surface for the casting instead of the non-uniform surface of blended polymers. From top and cross-sectional SEM images, surface flower-like pores, and bottom spherical pores interconnected each other are imaged. The pore shape was tunable from spherical to obovate by controlling the interfacial tension between the condensed water and the polymer solution. Based on the deep experimental observation, the formation mechanism for flower-like ordered hierarchical porous structure was proposed.