Rapid Fabrication by Lyotropic Self-Assembly of Thin Nanofiltration Membranes with Uniform 1 Nanometer Pores

Abstract

Nanostructured materials with precisely defined and water-bicontinuous 1-nm-scale pores are highly sought after as advanced materials for next-generation nanofiltration membranes. While several self-assembled systems appear to satisfy this need, straightforward fabrication of such materials as submicron films with high-fidelity retention of their ordered nanostructure represents a nontrivial challenge. We report the development of a lyotropic liquid crystal mesophase that addresses the aforementioned issue. Films as thin as similar to 200 nm are prepared on conventional support membranes using solution-based methods. Within these films, the system is composed of a hexagonally ordered array of similar to 3 nm diameter cylinders of cross-linked polymer, embedded in an aqueous medium. The cylinders are uniformly oriented in the plane of the film, providing a transport-limiting dimension of similar to 1 nm, associated with the space between the outer surfaces of nearest-neighbor cylinders. These membranes exhibit molecular weight cutoffs of similar to 300 Da for organic solutes and are effective in rejecting dissolved salts, and in particular, divalent species, while exhibiting water permeabilities that rival or exceed current state-of-the-art commercial nanofiltration membranes. These materials have the ability to address a broad range of nanofiltration applications, while structure-property considerations suggest several avenues for potential performance improvements.