Tuning substructure and properties of supported asymmetric triblock terpolymer membranes

Asymmetric poly(isoprene-b-styrene-b-4-vinylpyridine) (ISV) block copolymer membranes fabricated via self-assembly and non-solvent induced phase separation (SNIPS) process have drawn significant attention due to the simple processing method and the generation of high-quality isoporous ultrafiltration membranes. With the present study on SNIPS membrane substructure, we systematically varied membrane casting parameters to tune the cross-sectional morphologies of SNIPS membranes while simultaneously preserving top surface structure. Parameters such as polymer concentration, evaporation time, solvent ratio, and coagulation bath temperature were investigated to control transformation of commonly produced sponge-like cross-sectional morphologies into more open and permeable finger-like substructures. Membranes with sponge-like and finger-like substructures were then integrated onto nylon supports for enhanced mechanical properties. Hydraulic permeability tests at various pH conditions gave distinct open-state flux values for SNIPS membranes with different sublayer morphologies, while maintaining pH responsive functionality resulting from the poly(4-vinylpyridine) block. [Display omitted] •Block copolymer self-assembly based non-solvent induced phase separation is studied.•Dependence of asymmetric membrane substructure on casting conditions is tested.•Parameters tested include polymer concentration, evaporation time, and solvent ratio.•Results provide design guidelines for sponge- and finger-like substructure formation.