Conjugated Polymers Doped via Covalent Dopant-Molecule Adducts

在化学系大分子、超分子和纳米化学项目的支持下，约翰霍普金斯大学的Howard E. Katz教授和Paulette Clancy教授正在开发用于共轭聚合物掺杂的有机小分子。共轭聚合物是碳基大分子，含有由交替的双键和单键组成的长链。当通过移除或添加电子来改变双键排列时，聚合物中就会产生正电荷和负电荷，从而使它们能够像铜等金属一样导电。目前，共轭聚合物是最重要的一类材料，用于光电子器件，如移动设备和计算机中的LED（发光二极管）屏幕；也被用来保护这些电子元件不受外界电子干扰。在这项研究中，使用实验和计算方法相结合的系统研究将仔细检查这些聚合物系统中电子转移的机制，其中许多细节仍然未知。增加对这类系统的了解有可能导致与柔性电子和功率器件相关的具有可调谐电子特性的新型共轭材料。该项目的教育和推广活动将集中在约翰霍普金斯大学的工程创新项目上，目标是巴尔的摩市的低收入参与者。将为中学生提供编程训练营，目的是提高未来STEM（科学、技术、工程和数学）科学家的编程技能，特别针对女性和代表性不足的群体成员。本研究的目标是一系列噻吩基分子和低聚物，用于掺杂共轭聚合物。所提出的理论和实验研究旨在验证以下假设：(a)空穴/电子亲和的差异，(b)电荷分离的功，以及(c)中性共轭聚合物和共价离子加合物之间的离域/分布熵的自由能变化将导致电荷转移和导电性。用于加合物形成研究的噻吩基共轭分子和低聚物将根据硬度/柔软度进行选择，并有利于在非质子溶剂中形成成对电子、共价键（与电子转移相互作用相反），从而能够测试共价加合物最终是否作为共轭聚合物的电子转移剂。广泛的光谱和电化学表征方法将用于更深入地了解掺杂机制，以及结构变化如何影响掺杂水平、固态结构、电导率和塞贝克系数。与本研究相关的结果有可能导致更可靠的共轭聚合物掺杂策略，这是有机生物电子学和柔性导体进一步发展的关键挑战。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Professors Howard E. Katz and Paulette Clancy of the Johns Hopkins University are developing small organic molecules for use in doping of conjugated polymers. Conjugated polymers are carbon-based macromolecules that contain long chains consisting of alternating double and single bonds. When the double bond arrangements are changed by removing or adding electrons, positive and negative charges are created in the polymers that enable them to conduct electricity similarly to metals such as copper. Currently, conjugated polymers are the most important class of materials used for optoelectronic devices such as LED (light-emitting diode) screens in mobile devices and computers; also being used to protect such electronic components from outside electrical interference. In this research, systematic studies using a combination of experimental and computational approaches will closely examine the mechanism of electron transfer in these polymeric systems, a mechanism for which many details are still not known. Increased understanding of such systems has the potential to lead to novel conjugated materials with tunable electronic properties of relevance to flexible electronics and power devices. The education and outreach activities of this project will focus on the engineering innovation program at Johns Hopkins University targeting low-income Baltimore City participants. A boot camp on coding will be offered to middle schoolers with the goal of improving the programming skills of future STEM (Science, Technology, Engineering and Math) scientists, with the particular goal of reaching women and members of underrepresented groups.This research is targeting a series of thiophene-based molecules and oligomers for use in doping of conjugated polymers. The proposed theoretical and experimental studies are designed to test the hypothesis that the free energy change from (a) difference in hole/electron affinities, (b) work of charge separation, and (c) delocalization/distribution entropy between neutral conjugated polymers and covalent ion-adducts will lead to charge transfer and electrical conductivity. Thiophene-based conjugated molecules and oligomers for adduct formation studies will be selected with a range of hardness/softness and to favor paired-electron, covalent bond formation (as opposed to electron transfer interactions) in aprotic solvents to enable testing of whether the covalent adducts ultimately serve as electron transfer agents of conjugated polymers. Extensive spectroscopic and electrochemical characterization methods are to be used to gain a deeper understanding of the doping mechanism and how structural changes affect doping levels, solid-state structures, conductivity, and the Seebeck coefficient. The results associated with this research have the potential to lead to more reliable doping strategies in conjugated polymer- a key challenge for further development of organic bioelectronics and flexible conductors.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.