CAREER: Mechanics of Active Polymers with Dynamic Molecular Bonding

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This Faculty Early Career Development (CAREER) grant will use an integrated experimental-theoretical-computational approach to study the mechanical and interfacial properties of dynamic active polymers. Dynamic active polymers promise numerous applications ranging from healthcare to aerospace. As a notable example, adaptable liquid-crystal elastomers have the great potential to become a transformative actuator material that mimics the major functions of biological muscle (i.e., protection, actuation, self-healing), which will bring man-made machines closer to the natural capabilities of humans while greatly extending their applications. However, existing mechanics theories cannot fully accommodate the sophisticated coupling among the new chemistry, physics, and mechanics involved in these emerging active polymers. The project's theory will establish a clear connection between the dynamic molecular bonding and material energy dissipation, mechanical, and interfacial properties, which serves as an effective tool for the application-driven design and manufacturing with active polymers. The educational objective of this grant is to promote students' interest in engineering, enhance their learning of mechanics concepts, and prepare them with critical skills to meet the challenges in polymer engineering. Augmented reality-assisted active learning approach will be developed to improve students’ understanding of complex concepts. Annual workshops will be created to engage minority high school students with 4D printing of liquid-crystal elastomers.The specific goal of the research is to use adaptable liquid-crystal elastomers as a material platform to develop a mechanics of dynamic active polymer theoretical modeling and simulation framework that links the evolution of chain configuration with dynamic bonding to the network bulk and interfacial properties and use it to generate new designs of active structures with tailored energy dissipation, actuation, and healing capabilities. The research objectives include: (i) revealing the energy dissipation mechanisms, (ii) determining the stress-strain relationship, (iii) understanding the interfacial welding kinetics, and (iv) establishing a computational platform to design functional structures. The following fundamental questions will be answered: (1) why do liquid-crystal elastomers exhibit such an extraordinary energy dissipation, and how is it related to the material composition? (2) What is their stress-strain relationship when temperature-dependent chain interactions and dynamic bonding are both involved? (3) How is their interfacial welding different from the amorphous networks? The theory will serve as a cornerstone for the PI’s future studies on the design and characterization of structure-property relationships of newly developed active polymers. It also lays the foundation for the PI to investigate different forms of manufacturing and processing technologies of active polymers.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.