Formation of polyethersulfone film with regular microporous structure by water vapor induced phase separation

Polyethersulfone (PES) film with regular microporous structure was formed using dichloromethane as the solvent via water vapor induced phase separation (VIPS). The effects of solution concentration, atmospheric humidity and temperature, as well as molecular weight of PES on the surface morphology of the polymer film were investigated. The surface morphology characterized by SEM showed that the pore size reduced as the solution concentration increased. There was an optimum range of relative humidity for the formation of regular pore structure, which was from 60% to 90% at concentration of 20 g·L ^-1 and 20 °C. With the atmospheric temperature varied from 20 to 30 °C, the pore became larger and the space between pores increased. The pore size in the PES film with low molecular weight was smaller than that with high molecular weight.