Directed Self-Assembly of Block Copolymers Under Dynamic and Orthogonal Fields

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TECHNICAL SUMMARYThe need to control order in self-assembled block copolymers (BCPs) is well recognized from a technological perspective. At the same time, there is incomplete understanding of the complex field-matter interactions and dynamics with which BCPs undergo self-assembly under the action of external fields. The overall objective of this project is to build a body of knowledge that enables high fidelity control of orientational and positional order of BCP nanostructures by the application of external fields and to understand the mechanisms of such action. Specifically, this work pertains to: (1) the use of magnetic fields which vary in their intensity and direction and a function of time and/or location, so called dynamic fields, and (2) the use of more than one external field where the fields act along perpendicular directions, so called orthogonal fields. This work will be accomplished by the development of new materials and methods which permit fast biaxial alignment of BCPs under magnetic fields and effective coupling of multiple fields to a single system. New BCPs that display paramagnetic behavior and/or biaxial order will be designed and synthesized, to enable fast, biaxial alignment. New methods will be developed based on local perturbation of external magnetic fields using nanoparticles for dynamic field studies. Apparatus will be designed to enable studies of self-assembly under the simultaneous action of shear and magnetic fields.The specific objectives are: (1) development of BCPs that exhibit biaxial order and paramagnetic properties, (2) development and study of dynamic magnetic field-directed self-assembly, and (3) investigation of directed self-assembly under orthogonal magnetic and flow fields.NON-TECHNICAL SUMMARYBlock copolymers represent a technologically important class of synthetic materials and are made up of two or more different types of polymer molecules connected to each other. Depending on the chemical nature of each of the polymer molecules, the resulting materials consist of regularly arranged structures having dimensions of around 3-100 nanometers. The ability to control the position and alignment of these structures is highly desirable from a technological perspective. Compelling examples include applications of such aligned block copolymers for energy generation (e.g. photovoltaics) and water purification. This project addresses current gaps both in capability and fundamental understanding of alignment of block copolymer materials using external fields such as electric or magnetic. As such, it is in a position to impact or facilitate a broad spectrum of technologies with societal impact such as those mentioned above. This project involves a wide range of broader impacts including curriculum development for undergraduate and graduate students, K-12 outreach activities through Science Fair and Science Pathways programs, and summer research projects with science teachers. The PI will embark on specific initiatives aimed at improving recruitment of under-represented groups in collaboration with other stakeholders.