Lipid-polymer membranes: understanding ion transport through hybrid materials at the nanoscale

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Ions are small atomic or molecular species that carry a positive or negative charge. Many processes in nature, from the transmission of signals in brain cells to conversion of sunlight into energy by plants to the performance of batteries relies on efficient and controllable transport of ions from one place to another. In this project the PIs will develop a new class of materials that will yield improved methods to control and enhance ion transport. As the demands for efficient ion transport increase, materials with precisely tailored structures are needed to provide both pathways for charges to move as well as mechanical robustness. Polymers and phospholipids are two classes of materials which can self-assemble into structures with nanometer scale features, and in appropriate ratios their hybrids can generate novel nanostructures for ion transport. This project will underpin how nanostructures of hybrid materials and the size of the domains correlates with mechanical and transport properties. This innovative research project can generate new knowledge, resulting in the development of cost effective and benign approaches for the processing of nanostructured soft materials for many useful applications, including separations, water purification, and energy storage. The PIs will offer several educational activities. First, they will participate in a program called Polymers module for Middle-School Girls Learning About Materials (Mid-GLAM) summer camp. As part of this project, the PIs will prepare a day-long module, during which a full span of materials will be showcased. This will include demos in the PIs labs, giving students the opportunity to compare materials with different flow properties based on the underlying chemistry. The goal will be to teach, in a hands-on and engaging manner, how to engineer the properties of polymers which are used in everyday applications. This project will advance the fundamental understanding of self-assembly in block copolymer-phospholipid hybrid membranes and the corresponding impact on ion transport. While block copolymer and phospholipid self-assembly has received much attention individually, their hybrids can exhibit nanostructures and long-range domains which are not present in either of the two starting components. A key aim of this work is to understand how to harness the formation of stable, double gyroid morphologies to provide continuous pathways for ion transport. The hybrid materials will be investigated to deconvolute the roles of interfacial effects and intermolecular interactions. When confined to the nanoscale, ion mobilities can be greatly enhanced or suppressed which the PIs will probe through control of swelling, domain size, and interactions with the supporting substrate. The intermolecular interactions of ions with polymer will also be modulated through the charge density and species on the polymer backbone. Understanding what gives rise to large changes in diffusion under nanoconfined conditions is the second major aim. Finally, triggerable groups which respond to light and temperature will be incorporated into the block copolymer as a means to disassemble and interconvert between continuous and layered nanostructures to provide modulated transport. This research will provide fundamental insights into the self-assembly of complex soft materials, transport through nanostructured domains, and reversible structure formation of hybrid soft alloys. This work will be disseminated to undergraduate and graduate students in coursework including Biomolecular Materials and Kinetics in the Materials Science Department, where the self-assembly process and timescales will be discussed. The findings will also be disseminated both on campus and to the community through outreach projects including day camps for Girls Learning About Materials. Interest in STEM fields will be promoted to high school and middle-school girls, by introducing them to the exciting world of self-assembly and biological-synthetic hybrid 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.