Synthesis of guanidinium-functionalized amphiphiles for the exploration of chaotropic supramolecular nanoribbons

Abstract

Nanoscale self-assembly driven by the hydrophobic effect is of intense research interest due to the ability to synthesize complex, chemically diverse structures with molecular length scales. Supramolecular self-assemblies comprised of amphiphilic molecules have been engineered to achieve diverse applications, from drug delivery to 3D printing. The design of the component molecules in engineered assemblies are often bio-inspired, where structures are highly dynamic to respond to changes in their environment. Molecules within dynamic assemblies move rapidly due to molecular exchange and rearrangement, and the supramolecular structure is often only retained for a limited amount of time before breaking down. Aromatic amide (aramid) amphiphiles, which can form strong hydrogen bonding and pi-pi stacking between them, self-assemble into stable, mechanically strong nanofibers, in stark contrast to the assemblies that precede them. This study seeks to functionalize the aramid amphiphile nanofibers surface for the study of water dynamics by attaching a chaotropic guanidinium head group. This head group will disturb the hydrogen bonding network of surrounding water, causing a measurable change in water dynamics when analyzed using Overhauser Dynamic Nuclear Polarization. Guanidinylation was achieved, but future work must be done to create a kosmotropic analog. These two structures will be used to run parallel experiments to study the water dynamics in the local environment.