Studying the Processes of Assembly and Stimuli-Responsive Morphological Transformations in Solvated Macromolecular Nano-Assemblies

Northwestern University, Evanston IL

Investigators

Abstract

With funding from the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Nathan Gianneschi of Northwestern University and Lucas R. Parent of University of Connecticut examine how amphiphilic copolymers behave in water on the nanoscale. Amphiphilic copolymers are long chain molecules possessing both water-loving and oil-loving properties. Examples of common amphiphilic compounds include soaps and detergents. In this work, electron microscopy is used to observe molecular-scale movement during the self-assembly of amphiphilic copolymers in water. Experimental studies examine the pathways and intermediates for the assembly. Control of self-assembly has promise for applications such as optimized drug or cosmetic delivery vehicles, as functional elements in composites, as optical sensors, and in the transport of catalysts and reagents in industry and biology. Beyond research and mentoring in a laboratory, this project connects with ongoing school outreach efforts. Activities include Exploring Engineering and Spark annual summer camps for national STEM high school students and local middle school girls. Also, the da Vinci Program is designed to educate local secondary school teachers and administrators on increasing classroom STEM education. This work employs in situ liquid phase transmission electron microscopy techniques to study the dynamic processes of macromolecular nanostructures involving copolymers of N,N-dimethylacrylamide, N-isopropylacrylamide and/or n-butyl acrylate. Particular emphasis is placed on developing an understanding of the mechanisms and pathways of self-assembly/disassembly, kinetic trapping, phase changes and morphological transformations. Polymer syntheses are conducted using reversible addition-fragmentation transfer polymerization which enables control over molecular weight and polydispersity. Understanding control at the nanoscale has promise for the application of investigated amphiphilic copolymers as components capable of performing as optimized drug delivery vehicles and as functional elements in composites capable of mechanical or rheological responses. Additionally, such systems also have the potential to transport catalysts and reagents. Research associated with this award advances understanding of the fundamental process of self-assembly of discrete architectures from disperse polymers which is of significant interest not only to nanoscience community, but to polymer scientists in general. 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.