9:15 AM - NM06.11.04
Biomimetic Membranes from Membrane Protein-Block Copolymer 2D Materials for Aqueous and Vapor Applications
Yu-Ming Tu1,Benny Freeman1,Manish Kumar2
University of Texas at Austin1,The University of Texas at Austin2
Biomimetic and bioinspired membranes (BBMs) containing membrane protein (MP) channels and MP-mimic functionalized materials are innovative platforms to develop separation materials with uniform pore size distribution . Relative to commercial polymeric membranes, BBMs, which incorporate well-defined pore-forming structures that are designed to target precise molecular selectivity based on molecular size and shape of separating molecules, could be advantageous . Nevertheless, integrating MP-based membranes into current manufacturing technology for separations remains challenging. These constraints are possibly due to the compatibility of MPs and polymeric matrices, nanoscopic defects on resulting membranes, the usage of large amounts of functionalized porous materials, and time-intensive synthesis techniques.
In this study, we first fabricated MP-block copolymer (BCP) biomimetic membranes with three different types of pore-forming MPs with pore sizes of 0.8 nm, 1.3 nm, and 1.5 nm, respectively, for conducting targeted molecular separations. MPs were integrated into BCP matrices, poly(butadiene)-poly(ethylene oxide) terminated by carboxylic acid group (PB12-PEO8-COOH), forming two-dimensional (2D) crystals and nanosheets in a 2-hour organic solvent-based self-assembly method . The formation of 2D MP-BCP crystals indicates an optimized packing density of MPs into membrane matrices, which is ~2 orders of magnitude higher than that in proteoliposomes. The resulting three MP-BCP membranes manifested water permeability of ~300-2,000 (l m-2 h-1 bar-1), which is one to three orders of magnitude greater water permeability than commercial nanofiltration membranes, and still maintained a tunable solute selectivity inferred from pore sizes of three MP channels . Following this research, we further applied the modified fabrication process to create BBMs reconstituted with RsAqpZ (an aquaporin isolated from Rhodobacter sphaeroides)-BCP crystals  and sealing polymers for water desalination (>99 % rejection of 2,000 ppm NaCl).
To further explore applications of BBMs beyond aqueous separations and sustainable solutions for creating MP-based membranes with fewer defects, we developed a dehydration method and defect-sealing strategies. The tight defect-sealed MP membranes fabricating by the incorporation of nanoscopic defect-filling materials, photo-polymerizable diacetylene fatty acids, 23:2 Diyne PC, achieved >7-log (or >99.99999%) MS2 bacteriophage viral particle removal. Additionally, an efficient dehydration method using a chemical drying agent, Hexamethyldisilazane (HMDS), is investigated to preserve structures, integrity, and functionality of BBMs under dry conditions. The resulting dehydrated MP-based membranes exhibited a high water vapor transport rate (WVTR) of ~245 g m-2 hr-1, 1.5 times higher than commercial breathable fabrics . The preservation of MP-based membrane under dry conditions could extend the applications of BBMs such as protective fabrics for medical protections and barriers. The approach of combining MP channels and BCPs could offer the promise of incorporating porous structures into 2D material designs and developing separation materials for efficient transport and specific molecular-based separations in both aqueous and dry conditions.
1. Song, W., Tu, Y.M., Oh, H., Samineni, L. and Kumar, M., Langmuir 35, no. 3 (2018): 589-607.
2. Tu, Y.M., Samineni, L., Ren, T., Schantz, A.B., Song, W., Sharma, S. and Kumar, M., Journal of Membrane Science (2021): 118968.
3. Kumar, M., Ren, T., Song, W. and Tu, Y.M., U.S. Patent Application 16/414,517, filed November 21, 2019
4. Tu, Y.M.†, Song, W.†, Ren, T.†, et al., Nature Materials 19, no. 3 (2020): 347-354.
5. Erbakan, M., Shen, Y. X., Grzelakowski, M., Butler, P. J., Kumar, M., & Curtis, W. R. PloS one, 9, no. 1 (2014): e86830.
6. Oh, H.†, Tu, Y. M.†, Freeman, B.D. and Kumar, M. (In preparation)