CAREER: Stretchable Light-Emitting Polymers with Thermally Activated Delayed Fluorescence

第一部分：非技术概述人类集成的可穿戴和可植入电子设备，发光设备(如有机发光二极管，OLED)在显示、基于光的生命体征监测和疾病治疗、生物成像和光生物刺激细胞活动等应用中发挥着重要作用。对于这些设备来说，要具有可适应的皮肤/组织接触和长期兼容性，关键要求之一是具有类似组织的机械伸展能力。然而，到目前为止，所有可用的高性能发光无机和有机材料都相对刚性和脆性。这项研究将开发和研究一种将高效发光机制与橡胶类机械性能相结合的新型聚合物。这些新聚合物将通过新结构的化学合成和现有化学结构的物理工程来创造。通过对不同橡胶设计对发光性能影响的基础性研究，本研究将为这类新型聚合物提供设计原则，以实现发光器件的高效率和高延伸性。在这项研究的支持下，可伸缩发光技术可能会影响精密医疗、人机交互和人工智能等新兴领域。这项研究将丰富研究生和本科生的教育和培训，并通过与高中和芝加哥南部的科学与工业博物馆合作，促进未被充分代表的少数族裔(URM)学生参与STEM研究。第二部分：技术综述：可伸缩发光设备是人体集成电子设备新兴领域的重要组成部分，需要实现皮肤/组织样的机械性能和生物兼容性。然而，对于电致发光特性，对于结合机械可伸展的分子设计对光物理行为的影响的认识和理解仍然很少。本研究旨在创造一套材料设计原则，将应变耗散机制集成到一种最先进的发光材料类别--热激活延迟荧光(TADF)聚合物中，从而将皮肤般的可伸缩性与高电致发光效率相结合。具体地说，这项研究将探索和研究四种赋予TADF聚合物可延展性的一般方法：1)化学调节聚合物主链的柔韧性；2)通过化学方法增强聚合物侧链的柔韧性；3)物理松散链间堆积和相互作用；4)为TADF发射器的“宿主”聚合物赋予延展性。在这四种方法的新聚合物设计的支持下，本研究将通过多方面的实验表征和理论模拟相结合的方式，对TADF聚合物的热力学、力学和电致发光方面的结构-性质关系进行基础研究。这项研究还将培养未来本科生和研究生水平的劳动力，特别是与新兴的可穿戴和植入式电子行业相关的劳动力。该协会还将制定一项新的计划，将STEM研究带给芝加哥南区少数族裔比例较高的高中生，并为“芝加哥科学与工业博物馆”开发科学展品和公开讲座。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

PART 1: NON-TECHNICAL SUMMARY For human-integrated wearable and implantable electronics, light-emitting devices (such as organic light-emitting diodes, OLEDs) play important roles for applications such as displays, light-based vital-sign monitoring and disease therapy, bio-imaging, and optical bio-stimulation of cell activities. For these devices to have conformable skin/tissue contacts and long-term compatibility, one of the key requirements is to have tissue-like mechanical stretchability. However, all the high-performance light-emitting inorganic and organic materials available so far are relatively rigid and brittle. This research will develop and study a new class of polymers that combines high-efficiency light-emitting mechanisms with rubber-like mechanical properties. These new polymers will be created through both the chemical synthesis of new structures and the physical engineering of existing chemical structures. Through fundamental studies on the influence of different rubbery designs on light-emitting performance, this research will provide design principles for this new class of polymers for achieving both high efficiency in light-emitting devices and high stretchability. Enabled by this research, the stretchable light-emitting technology could impact the emerging areas of precision healthcare, human-machine interactions, and artificial intelligence. This research will enrich the education and training for graduate and undergraduate students, as well as promote the participation of underrepresented minority (URM) students in STEM research through partnerships with high schools and the Museum of Science and Industry in Chicago's South Side. PART 2: TECHNICAL SUMMARY Stretchable light-emitting devices represent an important component in the emerging area of human-integrated electronics that are desired to achieve skin/tissue-like mechanical properties and biocompatibility. However, for electroluminescent properties, the realization and understanding of the impacts of incorporating mechanically stretchable molecular designs on photophysical behaviors remain rare. This research aims to create a set of material design principles for integrating strain-dissipation mechanisms into a state-of-the-art category of light-emitting materials, that is "thermally activated delayed fluorescence" (TADF) polymers, so as to combine skin-like stretchability with high electroluminescence efficiencies. Specifically, this research will explore and study four general approaches for imparting stretchability onto TADF polymers: 1) chemically modulating the flexibility of polymer backbones; 2) chemically building flexibility onto polymer side chains; 3) physically loosening the interchain packing and interaction; 4) imparting stretchability onto “host” polymers for TADF emitters. Enabled by the new polymer designs from these four approaches, this research will carry out fundamental studies on the structure-property relationships that combine thermodynamic, mechanical, and electroluminescent aspects for TADF polymers by combining multi-aspect experimental characterizations and theoretical simulations. This research will also develop the future workforce at both undergraduate and graduate levels, with special relevance to for the emerging wearable and implantable electronics industry. The PI will also develop a new program for bringing STEM research to high school students in Chicago's South Side which have a high proportion of underrepresented minorities, as well as the development of scientific exhibits and public lectures for the “Museum of Science and Industry, Chicago”.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.