Collaborative Research: Highly ordered concentric multilayer nanostructures with probable liquid crystalline features from rigid sphere-rod amphiphiles in solution

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Non-technical Summary With support from the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program, both in the Division of Materials Research, this project combines experimental and computational research and education aimed at advancing the fundamental understanding of how rigid block copolymers behave and self-organize in solution to liquid crystals. Liquid crystal is a state of matter between fluid liquids and solid crystals, and broadly used as display devices in TV screens (LCD), cell phones and contact lenses. Block copolymers are formed by linking two or more different long chain polymers together. Different blocks often possess different properties such as solubility, which lead block copolymers to self-organize into various nanometer-scale structures and make them important materials in drug delivery, coating and lubrication. While block copolymers with flexible chains have been well studied, those with fully rigid components are poorly understood. Investigators from the University of Akron and Kent State University design and study fully rigid block copolymers with special shapes for each block. This fundamental investigation enables the researchers to understand how these rigid copolymers behave in solution, what types of supramolecular structures they can self-organize into, and how the structure formations are controlled by temperature, solvent, as well as the shape and architecture of copolymers. The team focuses in particular on exploring the possible liquid crystal features emerging from such rigid block copolymer assemblies. The team examines a probable new type of liquid crystals formed by rigid block copolymers and their potential applications as materials through a series of experiments and complementary computer simulations. Furthermore, the project engages graduate students, undergraduate students through the NSF-REU center at the School of Polymer Science and Polymer Engineering at the University of Akron, and high school students from the Akron-Kent areas in Ohio. Graduate students from both institutions supported by this grant can expand their experience by mutual visits, collaborative experiments and discussions. The team also visits local schools that are serving large numbers of minorities and encourage students to take science courses and pursue careers in STEM.Technical SummarySupported by the Solid State and Materials Chemistry program as well as the Condensed Matter Physics program, both in the Division of Materials Research, Professors Liu and Tsige at University of Akron, along with Professor Lavrentovich at Kent State University, team up to explore the self-assembly of fully rigid, sphere-rod shaped amphiphilic block copolymers. Such rigid copolymers demonstrate completely different assembly behaviors from the well-studied flexible block copolymers, by forming uniform, onion-like, multilayer concentric assemblies with identical, well-defined inter-layer distance. The assemblies respond to the change of solvent polarity, temperature and others by changing the number of layers while maintaining the overall structure and inter-layer distance. The project includes the following objectives which are pursued by combining experimental characterizations and computer simulations: (1) investigation of the mechanism and driving forces of this novel onion-like assembly and the reason for the uniform assembly size; (2) elucidation of the rational control of their size (number of layers) via changing solvent, counterions or temperature; (3) studying the effects of rod length, rod number, sphere size/shape, and rod orientation on the self-assembly, and (4) determination whether these onion-like supramolecular structures possess liquid crystalline features, and if so, how these unique features impact liquid crystal science and technology. The research expands the fundamental understanding of block copolymer materials (from flexible ones to rigid ones) and liquid crystals, as well as their potential applications as functional 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.