Locally unusual and tunable aromatic rings for pi-conjugated polymers

技术概述：该项目专注于探索pi共轭聚合物有机半导体，该半导体是由位于共轭聚合物主链上的不寻常的可调谐芳香段衍生而来。不寻常芳香性方面将体现在使用非苯类芳香族构建单元的研究中，即与苯、噻吩、吡咯等经典的6个pi电子芳香族核分离的重复单元。非苯类聚合物的焦点将集中在甲烷环烯上，这是一种非平面的10电子碳氢化合物，在有机化学中具有里程碑意义。环烯基聚合物的芳香性、扭转应变和无序性的基本问题将被研究，目的是优化所得的有效共轭长度和可溶聚合物的可加工性，以满足许多有机电子应用所需的溶液加工。确定这些共轭长度如何衰减的主要指标将是电子吸收和光致发光，但研究也将考虑计算、热学和载流子测量。可调芳构性方面将表现于光致变色构建块的使用研究中，即在紫外线或可见光照射下能够特定和可逆地改变电子结构的重复单元。提出了一种新的聚合物设计，将光化学开关事件与聚合物大分子构象变化解耦，从而为快速有效地调整电子性质作为应用光化学刺激的函数提供了前景。这些聚合物的电子特性将通过光诱导开关事件前后的电测量来评估。该计划的重点将放在复杂功能有机聚合物的探索性创造和其电子特性的详细表征上。在这项工作中确定的材料具有非常适合特定应用的电子和/或可加工性能（例如用作场效应晶体管、光伏或热电器件的有源元件），将通过约翰霍普金斯大学和外部的合作努力进行过渡。非技术总结：从有机聚合物中衍生的导电塑料作为更成熟的无机材料的可行替代品的开发具有重要的兴趣。有机聚合物更容易加工，使它们能够制成重量轻、面积大、甚至灵活的设备。这些塑料设备的应用范围从便携式光伏电池，发光显示器和可涂电子产品到新的生物相容性医疗材料。该项目专注于具有不同寻常的电学或光学特性、增强的加工能力或更大的环境稳定性的新型聚合物材料。与此同时，Tovar团队的研究人员将在先进聚合物系统的合成化学以及复杂的分析电化学和光谱技术方面获得宝贵的培训。第一手参与多学科研究合作的机会将提供更广泛的接触到材料化学可以带来新特性和潜在应用的许多前沿途径。Tovar小组将在巴尔的摩市内外的高中、本科和研究生中培养更多的有机电子研究机会，正如之前成功的活动所例证的那样。

TECHNICAL SUMMARY:This project is focused on exploration of pi-conjugated polymeric organic semiconductors that are derived from unusual and tunable aromatic segments positioned along the main chains of conjugated polymer backbones. The aspect of unusual aromaticity will be manifested in research on the use of non-benzenoid aromatic building blocks, that is, repeat units that depart from the classical 6 pi-electron aromatic nuclei of benzene, thiophene, pyrrole, etc. The focus of the non-benzenoid polymers will center on methano[10]annulene, a non-planar 10 pi-electron hydrocarbon established as a landmark in organic chemistry. Fundamental issues of aromaticity, torsional strain and disorder in annulene-based polymers will be investigated with the goal to optimize the resulting effective conjugation lengths and the processability of soluble polymers for solution processing necessary for many organic electronic applications. The primary metrics to determine how these conjugation lengths are attenuated will be electronic absorption and photoluminescence, but the research will also consider computational, thermal and charge carrier measurements. The aspect of tunable aromaticity will be manifested in research on the use of photochromic building blocks, that is, repeat units capable of specific and reversible changes in electronic structure upon exposure to UV or visible light. A new polymer design is proposed that decouples the photochemical switching event from polymer macromolecular conformational changes thereby offering the prospect for rapid and efficient tuning of electronic properties as a function of an applied photochemical stimulus. Electronic properties of these polymers will be assessed through electrical measurements before and after photoinduced switching events. The focus of this program will be on the exploratory creation of complex functional organic polymers and detailed characterization of their electronic properties. Materials identified in this effort as having electronic and/or processability properties well-suited for a specific application (e.g. for use as active components for field-effect transistors, photovoltaics or thermoelectrics) will be so transitioned through collaborative efforts already in place at Johns Hopkins and externally.NON-TECHNICAL SUMMARY:There is significant interest in the development of electrically conductive plastics derived from organic polymers as viable alternatives to more established inorganic materials. Organic polymers are much easier to process, allowing them to be fashioned into lightweight, large area, and even flexible devices. Applications for these plastic devices range from portable photovoltaic cells, light-emitting displays and paintable electronics to new biocompatible medical materials. This project is focused on novel polymeric materials having unusual electrical or optical properties, ehnanced processabilities or greater environmental stabilities. At the same time, researchers working in Tovar's group will gain valuable training in the synthetic chemistry of advanced polymer systems and with sophisticated analytical electrochemical and spectroscopic techniques. Opportunities to participate first-hand in multi-disciplinary research collaborations will provide broader exposure to many cutting-edge avenues where materials chemistry can lead to new properties and potential applications. The Tovar group will foster increased exposure to organic electronics research among high school, undergraduate and graduate-level students within Baltimore City and beyond, as exemplified by prior successsful activities.