Understanding the Roles of Charge Pattern and Charge Identity in Aqueous Micellar Assemblies Across Concentration Regime

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professor Donghui Zhang of Louisiana State University is studying structures of micellar assemblies of ionic polypeptoid block copolymers (BCP). Polypeptoid BCPs are structural mimics of naturally occurring polypeptides or macromolecules that contain chains of amino acids linked by peptide bonds. A unique feature of polypeptoid BCPs is that they lack extensive hydrogen bonding along the polymer backbone, making them soluble in many common solvents and amenable to thermal processing like conventional thermoplastics. As a result, they are very attractive materials for a wide range of biotechnological applications. In this project, systematic studies will be performed to understand how the structure of polypeptoid BCPs changes in solution as a function of the number and position of charged monomers in the polymer chain, as well as chemical identity of ionic monomers. If successful, this research could lead to new design rules and reliable protocols in producing polypeptoid-based nanostructures with controlled dimension and internal structure. This project will provide an excellent interdisciplinary training environment for student researchers at all levels. Participants will gain experience in areas ranging from polymer synthesis, solid phase synthesis, to structural characterization of polymer solutions using microscopic and scattering methods. The research team will continue participating in ChemDemo program at Louisiana State University by developing new demo kits focused on introducing polymer topics to K-12 students. Charge pattern and charge identity have been increasingly recognized for their significance in modulating the conformation, intra- and intermolecular interactions, phase behavior and biological function of biomacromolecules. There is comparatively much more limited understanding on how these molecular attributes can be manipulated to control the structure and interactions of non-natural polymers. This research will aim to fill this knowledge gap by investigating how charge pattern and chemical identity modulate the aqueous micellar assemblies of ionic polypeptoid block copolymers (BCPs) and the intermicellar interactions from the dilute to the semi-dilute regime. In Objective 1, polypeptoid BCP with varying charge pattern and chemical identity of ionic monomers (including polymer bound ions and counterions) will be designed and synthesized. Objective 2 will systematically study the roles of charge pattern in modulating the structural evolution of aqueous micellar assembly of these polypeptoid BCPs. Lastly, in Objective 3, the roles of chemical identity of ionic monomers including polymer bound ions and counterions in modulating the structural evolution of micellar structure of polypeptoid BCP from dilute to semi-dilute concentration regime will be investigated. This project has the potential to yield significant outcomes that will be of interest to the broad scientific community that studies solution polymer assembly, sequence-defined polymers, soft colloids, and biomimetic materials. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.