Precise dimension and shape control remains a great challenge in the design of covalent and supramolecular polymers. The proposed work focuses on controlling the size and shape of supramolecular polymers by carefully designing their monomeric subunits. The intellectual merit of the proposal is its goal to develop self-assembly modes that integrate mechanical and bonding forces, aggregation kinetics, and templating strategies to define the size and shape of supramolecular polymers in ways that emulate biological structures. These synthetic structures inspired by nature could enable a high level of structural control that is essential for novel functions. This program studies three different codes to precisely control supramolecular size and shape. In the one approach, buckled (non-spherical) vesicles are created using oppositely charged amphiphilic molecules. These fluid membranes will be used to template a thin metal layer or a semiconducting mineral into non-spherical three-dimensional structures. The second approach uses coiled-coil peptides that assemble into mushroom-shaped, polar aggregates. A charged polymer of precise length (e.g., DNA) will then template the formation of higher order assemblies with precise dimensional control. In a third approach, small molecules are used to assemble one-dimensional structures, in which morphology is controlled by the molecular structure and the growth kinetics. The principles learned from preliminary studies will be applied to form more complex architectures and supramolecular block copolymers. All three projects require chemical synthesis, electron microscopy and diffraction techniques, as well as coarse-grained modeling.
NON-TECHNICAL SUMMARY:
Learning from the complex structures seen in nature has been one of the major goals of modern materials research. The motivation is to design new, sophisticated materials such as artificial molecular motors for electronics, energy, or sensing devices and also biomedical materials to repair tissues and organs. The work cuts across physical sciences, life sciences, and engineering disciplines, and it is therefore an excellent platform for education of future scientists and for international collaborations. As a step toward the goal of complex functional materials, the proposed research involves precisely controlling the shape and size of several self-assembling systems. One approach involves the use of DNA molecules of precise length as external templates to dictate the dimension of components in synthetic materials. The other approach programs molecules to form nanostructures with non-spherical shapes similar to many viruses. The proposed work will have broad impact on the interdisciplinary education of graduate students in materials research, since each of the proposed projects operates at the interface of synthetic chemistry, physics, and materials science. Several students from underrepresented groups are receiving this training in the PI's laboratory and the proposed program could greatly extend this effort.
