EAGER: The First Steps toward Crosslinked Membranes with Non-Collapsible, Uniform Pores of Sub-nanometer Size: Synthesis of Building Blocks and Alignment of Nanotubular Assemblies

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This one-year EAGER award addresses the early stage fabrication of nanoporous membranes containing non-deformable pores with a uniform, subnanometer size. The resultant membranes will be used for water purification and desalination, as well as other size- and property-dependent molecular separations. The primary focus will be the use of a highly efficient, one-pot synthetic method for preparing large amount of macrocyclic building blocks that will then be used for engineering the membranes. The building blocks are macrocycles sharing a rigidified, cyclic backbone that contain a non-collapsible hydrophilic cavity of ~5-6 angstroms. Recent studies indicate that this class of macrocycles have a high propensity to associate into 1D tubular assemblies. Based on preliminary results, analogous macrocycles with side chains carrying polar terminal groups should self-assemble into nanoporous membranes. The alignment of the 1D tubular assemblies in the capillary pores of anodic alumina membranes will be probed. Computer simulation will be performed to investigate transport (nanofluidic) behavior of water within the nanopore under different external pressures and to evaluate the permeability of the membrane to various ionic species in a solvent as a function of size of nanopores. Optimally designed membranes are expected to reject most small molecules and ions and will be assessed as nanofiltration membranes for water desalination. The proposed research is highly interdisciplinary. Graduate and undergraduate students of various backgrounds will gain skills in multiple fields involving chemistry, materials science and the engineering of corresponding molecules and devices. Specifically, the educational impacts of this joint research include: (1) The unique opportunity to combine computer-aided design, synthesis, and characterization of molecular, supramolecular, and nanosized structures with the engineering of the corresponding materials and devices in the training of graduate students. (2) The program will involve undergraduate students, particularly those from groups traditionally underrepresented in sciences and students, who have limited exposure and access to the latest developments in the corresponding fields. (3) The research results will not only be published in highly visible journals to broadly disseminate this work to scientific society at large, but more importantly, will lead to many practical applications. Insights obtained from the construction of nanosized building blocks and the assessment of their 1D assembly will in turn will help the development of concepts generally useful for addressing other problems in the field of chemical and biological separation.