Nano- and micro-scale structures that are constructed through the non-covalent assembly of organic molecules have enabled the rise of life in all its diversity, as these macromolecular architectures are found in innumerable forms and are able to perform remarkable functions. For example, lipid bilayers and their protein partners regulate their internal pH and respond to changes in environmental conditions by controlling the permeation of ions, small molecules, vitamins, and nutrients. The functional responsive performance of natural membranes and compartments far exceed the most advance artificial membranes and structures. This is despite modern polymerization methods enabling chemists to prepare functionalized amphiphilic block copolymers with control over molecular weight and the incorporation of responsive moieties. Control at the nanoscale has promise for the application of these systems as components capable of performing as optimized drug or cosmetic delivery vehicles, as functional elements in composites capable of mechanical or rheological responses, optical responses, or in the transport of catalysts and reagents. Indeed, a transformation in physical form (e.g. from dispersed polymer to assembly, or from one morphology to another) in turn imparts a functional response in a system, such as a color change, a rheological change, or the release or capture of molecular cargo. To optimize and harness these systems, we require a deeper understanding of the assembly and transformation processes. We propose an experimental approach, seeking to directly observe molecular-scale assembly dynamics and kinetics in situ, by liquid phase transmission electron microscopy. The work will involve fundamental studies into the mechanisms, pathways, and intermediates for the assembly and transitions of various archetypal amphiphilic block copolymer assemblies (e.g. spheres, rods, and vesicles). This requires microscopy in the solution phase, with the resolution to observe translational motion of molecules and materials, reactivity, and assembly into larger nano- and micro-scale materials. We aim to observe the transport and dynamics of dispersed amphiphiles and their assemblies in water/solvents, developing an understanding of the mechanisms and pathways of self-assembly/disassembly, kinetic trapping, phase changes, and morphology transformations.
|Effective start/end date||8/1/19 → 7/31/22|
- National Science Foundation (CHE-1905270)
Transmission electron microscopy