CAREER: Thermomechanical Property Control of Confined Conjugated Polymeric Thin Films

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This project is jointly funded by the Polymers Program in the Division of Materials Research and by the Established Program to Stimulate Competitive Research (EPSCoR).NON-TECHNICAL SUMMARYUnderstanding the dynamics of electronically active polymeric materials is crucial for the development of next-generation foldable and deformable electronic devices. It is also envisioned that in the near future implantable electronic devices could provide unique interfaces between the human body and emerging electronics, thus restoring lost human function, such as hearing, vision, and bodily movement. However, there are no established design roles to understand, control, and predict the softness and pliability of such new electronically active materials. This project aims to address this challenge by developing fundamental new knowledge on the dynamics of polymer macromolecules and thus provide a pathway to make ultra-soft electronics that can enable the next generation of soft electronic devices for future wearables and implants. The researchers at the University of Southern Mississippi will develop, test, and validate new electronically active polymers using special instrumentation and develop new models to predict and control their softness. The research will include development of design rules to achieve tunable control of the electronic and mechanical properties of semiconducting polymers by measuring, understanding, and manipulating their mechanical properties and molecular entanglement behavior.In addition to research involvement of graduate and undergraduate students, the educational effort of the project would implement an integrated and curiosity-driven virtual and in-person education platform on polymeric and optoelectronic materials to local K-12 students, including school districts comprising a majority of underrepresented students. Broader impacts will also include a focused Southern U.S. X-ray/neutron scattering workshop to bring new scientific techniques to the local scientific community.TECHNICAL SUMMARY Organic semiconductors based on conjugated polymers exhibit unique optoelectronic properties and have been widely applied in a broad range of applications for efficient lighting, health care, energy harvesting, and storage. Despite promising advances in their optoelectrical properties, the ability to predict and control thermomechanical properties is lagging behind. Thus, the overall goal of this project is to develop new design rules to achieve tunable control of the electronic and mechanical properties of conjugated polymers by measuring, understanding, and manipulating their glass transition temperature as well as their molecular entanglement behavior. Researchers at the University of Southern Mississippi will target the following goals: 1) accurately determine the glass transition temperature for conjugated polymers and its influence on the mechanical properties in both device-relevant thin-film confined states and bulk state; 2) illustrate the design rules for engineering highly entangled polymer chains to understand the role entangled semi-rigid chains have on final fracture behavior of free-standing thin films under confinement; and 3) understand the deformation mechanism of semi-rigid conjugated polymers using multimodal in-situ spectroscopy and scattering techniques, and thus guide the design of future deformable electronics. The fundamental knowledge gained through this project will lead to precise control of the thermomechanical properties of conjugated polymers, thus contributing to the development of future soft robotics, implantable health care, and robust energy harvesting devices..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.