Highly Packed Artificial Water Channels in Lamellae Block Copolymer Film

Highly packed artificial water channels in lamellae block copolymer film

Yue-xiao Shen, Manish Kumar*

Department of Chemical Engineering, The Pennsylvania State University, University Park, PA, 16802

*Corresponding Author, Tel.: (814)-865-7519; email address: manish.kumar@psu.edu

The discovery of the high permeability of water channel proteins aquaporins (AQPs) and their analogs carbon nanotubes (CNTs) have created an explosion in materials where they are incorporated to develop novel filtration membranes.¹ AQPs can conduct single channel water transport with ~3 billion water molecules per second and are being extensively studied in biomimetic membranes for desalination. The bottlenecks of large-scale application are high cost of membrane protein production, questions regarding stability, and challenges in membrane fabrication.¹ CNTs based membranes have much better chemical stability, but the difficulty in fabricating vertically aligned and subnanometer diameter CNTs and low packing density in membranes also hold back commercial applications.²

Artificial water channels are alternative bioinspired analogues of AQPs created using synthetic chemistry.^1,3 They combine the advantages of biological channels and CNTs and improve upon them through their relatively simple synthesis and chemical stability. In the latest study, we have reported that the newly designed peptide-appended pillar[5]arene (PAP) artificial water channels (Figure 1a) have similar water conductance compared to AQPs and CNTs.⁴ Furthermore, they are capable of aligning and forming highly packed two-dimensional arrays in lipid membranes.⁴

In this article, we will present a new method to form porous and aligned PAP channels in the self-assembled lamellae block copolymer (BCP) films. We select polybutadiene-polyethylene oxide (PB-PEO) diblock copolymers, because PAP channels have been seen to be functional in the polymersomes (Figure 1b). PAP channels have tubular transmembrane structures and an outer surface which can favorably interact with the hydrophobic region of BCPs. Based on this theory, we expect that the PAP channels can be densely packed with orders in these lamellae films after annealing (Figure 1c).⁵ We propose to utilize this functional porous film to fabricate composite desalination membranes.

Reference

1              Shen, Y.-x., Saboe, P. O., Sines, I. T., Erbakan, M. & Kumar, M. Biomimetic membranes: A review. J. Membr. Sci. 454, 359-381 (2014).

2              De Volder, M. F. L., Tawfick, S. H., Baughman, R. H. & Hart, A. J. Carbon Nanotubes: Present and Future Commercial Applications. Science 339, 535-539 (2013).

3              Barboiu, M. & Gilles, A. From Natural to Bioassisted and Biomimetic Artificial Water Channel Systems. Acc. Chem. Res. 46, 2814-2823 (2013).

4              Shen, Y.-x. et al. Highly permeable artificial water channels that can self-assemble into two-dimensional arrays. Submitted to PNAS.

5              Li, M. & Ober, C. K. Block copolymer patterns and templates. Mater. Today 9, 30-39 (2006).