Locally unusual and tunable aromatic rings for pi-conjugated polymers

技术概要：本项目的重点是探索π共轭聚合物有机半导体，其衍生自位于共轭聚合物主链沿着的不寻常和可调芳族链段。 不寻常的芳香性的方面将表现在使用非benzenoid芳族结构单元的研究，即，重复单元，从经典的6 π电子芳香核的苯，噻吩，吡咯等非benzenoid聚合物的重点将集中在methano[10]轮烯，非平面10 π电子烃建立作为有机化学中的里程碑。 基于轮烯的聚合物中的芳香性、扭转应变和无序的基本问题将被研究，目标是优化所得的有效共轭长度和许多有机电子应用所必需的溶液加工的可溶性聚合物的可加工性。 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，但研究还将考虑计算，热和电荷载流子测量。 可调芳香性的方面将体现在对使用光致变色构建块的研究中，光致变色构建块是指在暴露于紫外线或可见光时能够在电子结构中发生特定和可逆变化的重复单元。 提出了一种新的聚合物设计，其从聚合物大分子构象变化中提取光化学转换事件，从而提供了快速和有效地调节作为所施加的光化学刺激的函数的电子性质的前景。 这些聚合物的电子特性将通过光致开关事件之前和之后的电测量进行评估。 该计划的重点将是复杂功能有机聚合物的探索性创造及其电子特性的详细表征。 在这项工作中确定的具有电子和/或加工性能的材料非常适合于特定的应用（例如，用作场效应晶体管，光电或热电的有源元件），将通过在约翰霍普金斯和外部已经到位的合作努力进行过渡。非技术性总结：在开发由有机聚合物衍生的导电塑料作为更成熟的无机材料的可行替代品方面有很大的兴趣。 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、发光显示器和可涂漆电子产品到新的生物相容性医疗材料。该项目的重点是新型聚合物材料具有不寻常的电气或光学性能，先进的加工能力或更大的环境稳定性。 与此同时，在Tovar小组工作的研究人员将获得先进聚合物系统合成化学以及复杂的分析电化学和光谱技术方面的宝贵培训。参与多学科研究合作的第一手机会将为材料化学带来新特性和潜在应用的许多前沿途径提供更广泛的接触。 托瓦尔集团将促进增加接触有机电子研究高中，本科和研究生水平的学生在巴尔的摩市内外，如先前的成功活动的例子。

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.