Stabilizing Organized Surface Structures in Casting Solutions of Ionic Block Copolymer Membranes

Additive-free membranes might be more convenient in some applications. Therefore, isoporous membranes from ionic diblock copolymer polystyrene-block-poly (acrylic acid), (PS-b-PAA), were prepared via self-assembly and nonsolvent induced phase separation (SNIPS) process without any foreign additives. A key step in the fabrication of ionic block copolymer membranes through SNIPS technique is the maintenance of the ordered micelles assembly during the phase inversion step. Different strategies were utilized to preserve the uniformity and regularity of the micelles assembly upon immersion precipitation. The organized micelles assembly in casting solutions and surface morphology of membranes were characterized by solution small angle X-ray scattering (solution SAXS) analysis and field emission scanning electron microscope (FESEM), respectively. Using the low-temperature water bath was determined as the most effective way to obtain additive-free isoporous PS-b-PAA membranes.