Honeycomb-Structured Porous Films Controlled by the Temperature of Water Bath

The highly ordered porous films were fabricated from the solution of polystyrene with one carboxyl terminal group in carbon disulfur in a chamber with a water bath. It is found that the pore size can be readily controlled by changing the temperature of water bath. The pore size increases with an increase in the water-bath temperature in a given range. And the porous film from the "dilute" solution can be readily formed even at a low relative humidity (RH), while the porous film from the "concentrated" solution can be fabricated only at a rather high RH. The regularity of porous film becomes better at the higher RH and higher concentration. It suggests that there exists a synergetic effect of solution concentration and RH on the formation of porous film. These phenomena are explained by the slow evaporation rate of the solvent under the conditions.