Journal of Membrane Science, 2018, vol 566pp. 25-34
Isoporous membranes with pore size smaller than 10 nm are significantly important for molecular separation. However, preparation of such membranes from process containing self-assembly and non-solvent induced phase separation (SNIPS) is challenging, and only few works were conducted until now. Herein, we described that membranes with pore size down to 8.6 nm and pore density up to 1.3 × 1015/m2 were generated from the well-defined SNIPS with the specially designed additive, which interacted selectively with poly(4-vinylpyridine) and facilitated the phase separation when membranes were prepared from the polystyrene-block-poly (4-vinylpyridine) (S4VP). Interaction of the additive with S4VP in casting solutions was probed by nuclear magnetic resonance (NMR), which was ascribed to the reason for the enhanced phase separation that was inspected by small angle X-ray scattering (SAXS). The effect of preparation conditions, such as the ratios of the additive to P4VP, the compositions of solvent, and the polymer concentrations on membrane formation were systematically investigated. The morphologies and pore size on membranes were analyzed by scanning electron microscope (SEM), and their rejections to proteins of varied size and charges were finally determined. Our method showed herein has opened an access to the preparation of isoporous membranes with sub-10 nm pores that were desirable for molecular separation.