AbstractThe molecular design of block copolymer membranes has been widely used as a toolbox to explore the functionality and pore size of the membranes. However, the study of membrane performance as a function of systematic change of the pore size has not been widely explored so far. We prepared an integral asymmetric isoporous membrane on the example of polystyrene-block-poly(2-hydroxyethyl methacrylate) (PS-b-PHEMA) membranes using an easily scalable method which combines the block copolymer self-assembly and nonsolvent induced phase separation. The pore size of the PS-b-PHEMA membrane was tuned via two post treatment methods, a chemical postmodification by urethane chemistry and a physical post treatment by thermal annealing, respectively. At pH 7.4 bovine serum albumin (BSA), hemoglobin (Hb) and catalase (Cat) do not adsorb on the prepared membranes. The retention of BSA, Hb and Cat from their aqueous solution was investigated and the ideal selectivities of three protein pairs , and were calculated. The and of the postmodified membranes were significantly higher than those of the PS-b-PHEMA membrane. This study is the first to demonstrate that the size selectivity of a SNIPS membrane can be enhanced by controlled physical and chemical post treatment of a SNIPS membrane.