Toward the Fabrication of Advanced Nanofiltration Membranes by Controlling Morphologies and Mesochannel Orientations of Hexagonal Lyotropic Liquid Crystals

Abstract

Water scarcity has been recognized as one of the major threats to human activity, and, therefore, water purification technologies are increasingly drawing attention worldwide. Nanofiltration (NF) membrane technology has been proven to be an efficient and cost-effective way in terms of the size and continuity of the nanostructure. Using a template based on hexagonal lyotropic liquid crystals (LLCs) and partitioning monomer units within this structure for subsequent photo-polymerisation presents a unique path for the fabrication of NF membranes, potentially producing pores of uniform size, ranging from 1 to 5 nm, and large surface areas. The subsequent orientation of this pore network in a direction normal to a flat polymer film that provides ideal transport properties associated with continuous pores running through the membrane has been achieved by the orientation of hexagonal LLCs through various strategies. This review presents the current progresses on the strategies for structure retention from a hexagonal LLCs template and the up-to-date techniques used for the reorientation of mesochanels for continuity through the whole membrane.

Lyotropic Liquid Crystal-Based Membranes for Water Remediation: Fabrication, Characterization and Performance Evaluation

“…The pore size is likely to be associated with the hexagonal water channel with a diameter of ∼ 5 nm, as has been previously reported. 25 , 47 − 49 …”

Homeotropic Self-Alignment of Discotic Liquid Crystals for Nanoporous Polymer Films

“…Efforts to develop nanostructured thin films based on polymerizable discotic liquid crystals has become a well-established research area, which has already produced a valuable basis for future applications such as membrane filtration or ion-selective layers. 10 , 11 However, up to now, most of the work has been performed on nonaligned nanostructured morphologies, with a few exceptions. 12 , 13 In order to further develop this approach toward nanoporous membranes that can potentially be used as an active layer for nano- and ultrafiltration, an effective method needs to be developed to obtain pores that span the entire thickness of the film.…”

Nanoporous Polymers Based on Liquid Crystals

“…For the fabrication of nanoporous polymers, the use of both lyotropic liquid crystals and thermotropic liquid crystals has been reported. When lyotropic LCs are used, the size of the pores in the polymerised network is determined by the amount of water (solvent) present in the organised mesophase; this approach has been reviewed by Wang et al [ 44 ].…”