2D Interfacial Crystallization Stabilized by Short-Chain Aliphatic Interfaces

We report the formation of interface sealing crystalline sheets based on amino acid and peptoid-monomer amphiphiles. This process, interfacial crystallization (IFC), is demonstrated using a range of halide salts of amidated peptoid monomers and amino acid amide bases with varied aliphatic sidechains. In our investigation, we identified that sufficient dynamic freedom of attached sidechains is a crucial design principle underpinning the viability of IFC for a given molecule. In addition, our results indicated that a combination of ionic coordination, hydrogen bonding and dispersion interactions all contribute significantly to the formation of these structures, and they are consistent with a hypothesis of interfacial ion migration playing a critical role in structure formation. A comprehensive range of techniques, including AFM, FT-IR, TOF-SIMs, X-ray crystallography, salt exchange experiments, quantum mechanical (QM) calculations and molecular dy-namics (MD) simulation studies were used to characterize this phenomenon. The formation of these hierarchical nanostructures, and the simplicity of the chemistry involved, suggests that IFC may have applications in formation of 2D supramolecular materials and barriers.