CAREER: Building Hierarchical Polymers with Light to Unify Softness, Resilience, and Conductivity

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NON-TECHNICAL SUMMARY:Polymers have become ubiquitous in our daily lives owing to their inherent low cost and tunable properties. Their versatility is a direct result of their chemical composition and the way in which the molecules are connected. However, current control over both composition and structure pales in comparison to that found in natural systems, which have an evolved hierarchical architecture tuned for specific functions. As such, synthetic materials often interface poorly with biological ones, precluding, for example, the ability to study and treat disease. This program targets the preparation of soft and resilient (i.e., strong and stretchy) polymers that mimic natural tissue (e.g., skin, heart, and lung), while additionally imparting electrical conductivity to facilitate communication between modern electronic devices and biological systems. Improving the communication between devices and biology will allow scientists and doctors to better study and control natural functions in an emergent area of research: bioelectronics. The proposed materials build off a foundation of industrially relevant polymers by introducing new molecular architectures to increase softness for better interfacing with natural systems without compromising strength. Moreover, low-energy visible light will be leveraged to define when and where chemical reactions take place, enabling the fabrication of hierarchical structures in a process that is amenable to future implementation in 3D printing.Ultimately, to solve these challenging interdisciplinary scientific problems requires a well-prepared diverse scientific workforce, and diversification in STEM requires education and engagement at an early stage of professional development. Therefore, as part of this project a first-year undergraduate polymer research course will be developed at the University of Texas at Austin, along with a hands-on polymer activity for students at local middle/high schools in East Austin with large populations of underrepresented groups. Overall, the proposed research serves the national interest by promoting the progress of science through fundamental discovery, educating the next generation STEM workforce, and facilitating the development of advanced materials that will improve health and welfare.TECHNICAL SUMMARY:Complementary strategies to generating hierarchical conductive polymers with tissue-like softness and resilience (strength + elasticity) are described. While synthetic polymers have become ubiquitous in our daily lives, control over their composition, structure, and morphology pales in comparison to that found in nature, limiting functionality and possible end-use applications. Softness and resilience are two mechanical parameters expressed by a number of biological materials (e.g., skin, heart, and lung tissue) to prevent rupture, yet harnessing these together synthetically remains elusive. Moreover, communication through modern technology relies on electronic transport, while biological systems operate via the movement of ions. These mechanical and communication discrepancies have hampered the study and control of biological processes via bioelectronics for medicine. To close the technology-biology gap, a bottom-up approach using rapid spatiotemporally controlled light-based polymerization chemistry to access materials with complex architectures and tailorable mechanical and transport properties are proposed. The materials sit in one of two categories: 1) ABA triblock copolymers and 2) interpenetrating polymer networks (IPNs). Multiple levels of hierarchical structure across length scales within these materials will provide the missing links to unify softness, resilience, and conductivity, unveiling critical, yet fundamental, structure-property relationships to inform further materials optimization. Given the generality of block copolymers and IPNs, and emerging interest in electronic/ionic transduction for bioelectronics and light-based chemistry for 3D printing, the scientific discoveries from the proposed research will lay a foundation from which a myriad of next-generation applications will emerge (e.g., bioelectronics and soft robotics)..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.