Selective swelling blends of block copolymers for nanoporous membranes with enhanced permeability and robustness

Block copolymers (BCPs) are important precursors to produce membranes with well-defined porosities. However, it remains challenging to prepare robust and affordable BCP-based membranes. In this work, cheap commodity styrene-butadiene-styrene (SBS) elastic triblock copolymers are mixed with polystyrene-block-poly (2-vinylpyridine) (SV) block copolymers in solutions, leading to macroscopically stable blend films upon casting because of the compatibilizer effect of PS existing in both copolymers. By soaking the blend films in ethanol, the microdomains of poly(2-vinylpyridine) are selectively swollen and cavitated upon drying, resulting in a hierarchical structure with perforated SV phases interwoven with the SBS phases. The blend membranes with 30% SBS exhibit improved water permeability and mechanical robustness due to the presence of elastic SBS compared to neat SV membranes; meanwhile, the rejections of the blend membranes remain largely unchanged. Moreover, the blend membranes exhibit a pH-responsive function, and homoporous SV regions are obtained by pre-aligning the SV phases.