Self-assembled materials are highly attractive for next-generation membranes as they circumvent the limitations of pathway tortuosity and size-dispersity of transport-regulating features found in conventional membranes. Here we address two disparate efforts to realize such membranes, and detail progress towards the promise of highly selective and highly permeable membranes for water purification. In the first case, we use self-assembly of crosslinkable thermotropic discotic mesophases to generate highly ordered nanopores of ~1-2 nm diameter. The pore diameter is defined by the characteristics of a templating core molecule around which the columnar nanostructure of the mesophase are self-assembled. High fidelity alignment of the structures can be performed using magnetic fields, or, more readily, by the use of appropriate confining surfaces during self-assembly of the material. The second case is based on the use of a crosslinkable lyotropic mesophase in which transport occurs in the water-continuous medium surrounding hexagonally packed cylindrical nanostructures. Structural integrity is preserved by cylinder-to-cylinder crosslinks, despite the water-continuous nature of the system. Results of molecular dye-based nanofiltration studies show that both membranes are highly selective at the 1-2 nm length scales. However while the thickness-normalized water permeabilities of membranes derived from the discotic mesophase are on the order of 0.3 LMH.μm.bar<sup>-1</sup>, that of membranes derived from the lyotropic system are a factor of ~60 higher, 18 LMH.μm.bar<sup>-1</sup>. We discuss strategies for scalable fabrication of both systems, in particular, addressing the challenge of controlling the active layer thickness in the presence of mechanical support membranes.

Next-generation nanofiltration membranes based on aligned and bicontinuous self-assembled systems

2019 Spring National Meeting

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