Selective Swelling of Block Copolymers: An Upscalable Greener Process to Ultrafiltration Membranes?

Block copolymers (BCPs) have long been pursued as precursors to nanoporous membranes, and selective swelling-induced pore generation has emerged as an extremely simple strategy to BCP membranes with both well-defined nanoporosity and inherently functional surfaces. In this Perspective, we briefly discuss the principles of this pore-making method and summarize its key features and most recent progress on thus-produced ultrafiltration membranes. Exciting results toward the upscaling of this method are highlighted: the large-scale, affordable synthesis of polysulfone-based BCPs and the continuous manufacturing of BCP membranes by melt extrusion coupled with microwave-boosted selective swelling. Importantly, we reveal the "greener" nature of this selective swelling process compared to conventional phase-inversion methods as it involves less aggressive solvents and produces no wastewaters. An outlook on the remaining challenges and future efforts to push selective swelling to real-world applications is also presented.