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

• Published in: ACS nano 2021-05, Vol.15 (5), p.8192-8203
• Main Authors: Zhang, Yizhou, Dong, Ruiqi, Gabinet, Uri R, Poling-Skutvik, Ryan, Kim, Na Kyung, Lee, Changyeon, Imran, Omar Q, Feng, Xunda, Osuji, Chinedum O
• Format: Article
• Language: English
• ISSN: 1936-0851; 1936-086X
• DOI: 10.1021/acsnano.1c00722

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 ∼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 ∼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 ∼1 nm, associated with the space between the outer surfaces of nearest-neighbor cylinders. These membranes exhibit molecular weight cutoffs of ∼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.