Facile preparation of porous polymeric sheets with different sizes of pores on both sides using spontaneous emulsification

Abstract Sheets have several advantages over conventional material forms such as gels and particles in medical fields, owing to their large contact area relative to drug-targeting sites, their shape and size being easily adjustable, and easy handling in surgery. Although it is possible to alter the properties of sheets, including their biocompatibility, strength, flexibility, and degradation rate, by both the porosity formation and blending of multiple substances, a facile and controllable method for forming porous structures in sheets has not been established. In the present study, we successfully demonstrate that porous sheets with different pore sizes on both sides can be formed only by statically leaving the water/organic solvent biphasic system dissolving a sheet-forming polymer in the presence of a block copolymer. We found that (1) the combination of the hydrophobic block of a surfactant and hydrophobic material-forming polymer, (2) temperature, and (3) relative humidity significantly affects the morphology of materials prepared by controlling the spontaneous emulsification phenomenon. Furthermore, water vapor condensation at the air–liquid interface resulted in the formation of water droplets and micropores on the surface of the sheet. We expect that the method presented can provide a platform for the development of materials whose functions can be significantly changed depending on the pore size, such as drug-release materials and cell culture materials.