Understanding the Roles of Intra- and Interchain Order on Spin-Dependent Electronic Processes in Self-Assembled Conjugated Polymer Aggregates

有了这个奖项，化学系的大分子，超分子和纳米化学计划正在支持新墨西哥州大学的约翰·格雷教授研究自组装聚合物系统中的自旋相关过程。共轭聚合物是由吸收光和传导电荷的基本分子重复单元组成的大链，使其成为下一代光电应用的优秀候选者。例如，这些所谓的“塑料”半导体用于太阳能电池和发光显示器，由于它们在过去10年中不断提高的效率和相对较低的成本，它们最终可能取代现有技术。 聚合物链在薄膜中折叠和包装的方式对有机太阳能电池和发光器件（OLED）的整体性能具有显著影响。 拟议的研究将使用新的策略来制造有序的聚合物结构，并研究电荷是如何形成的，以及如何在所得薄膜中更有效地产生电流。 此外，PI和他的NSF赞助的研究生积极参与正在进行的教育和研究基础设施发展计划在新墨西哥州的大学。这些活动包括与当地综合纳米技术中心（CINT）协调，通过与CINT工作人员科学家合作，增加本科生和研究生研究人员的参与。 学生通过撰写用户提案来参与，这些提案经过同行评审，从而为设计和执行独立的研究项目提供宝贵的经验。 最后，学生参与者在对国家利益至关重要的学术领域获得宝贵的和多样化的技能。共轭聚合物材料中不同自旋的电中性（激子）和带电（极化子）状态之间的相互作用和相互转换对它们在尖端光电器件（如太阳能电池）中的整体性能具有重要影响。 尽管这些方法的结果强烈依赖于聚合物结构，但已经证明难以从常规聚合物官能形式（即，体薄膜）。 这种困难源于聚合物固有的分子量多分散性导致的形态不均匀性。 拟议的研究旨在克服异质性效应，以了解分子结构如何调节激子和极化子自旋态的相互作用和相互转换。 自组装方法被用来制造定义明确的聚合物聚集体超分子纳米结构，可以利用选择性地控制构象和包装（链内和链间）的顺序和电子耦合。 新墨西哥州大学的Grey小组率先采用这种方法来直接在聚合物聚集体中进行激子耦合和极化子相互作用，这些聚合物聚集体在拟议的研究中被用来解决长期存在的基本问题，包括聚合物半导体中的自旋状态交换相互作用和交叉。 这项研究还需要通过引入敏感和选择性的电场和磁场依赖的分子光谱和成像技术来询问单个聚合物纳米结构中不同自旋态的命运和相互作用的新方向。 该研究旨在建立设计规则，以可靠地调整超分子组装体中的精细聚合物链包装和顺序，以理解和控制交换相互作用和自旋状态相互转换，从而改善材料性能。

With this award, the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division is supporting Professor John Grey of the University of New Mexico to study spin-dependent processes in self-assembled polymeric systems. Conjugated polymers are large chains consisting of a basic molecular repeat unit that absorb light and conduct charges making them excellent candidates for next-generation optoelectronic applications. For example, these so-called 'plastic' semi-conductors are used in solar cells and light emitting displays, which may eventually replace existing technologies owing to their ever increasing efficiencies over the last 10 years and relatively low cost. The ways in which the polymer chains fold and pack in thin films has a significant impact on the overall performance of organic solar cells and light-emitting devices (OLEDs). The proposed research will use new strategies to fabricate ordered polymer structures and study how electrical charges are formed and how electrical current can be generated more efficiently in the resulting films. In addition, the PI and his NSF-sponsored graduate students actively participate in ongoing educational and research infrastructure development programs at the University of New Mexico. These activities include coordinating with the local Center for Integrated Nanotechnologies (CINT) to increase the participation of undergraduate and graduate researchers through collaboration with CINT staff scientists. Students take part by writing user proposals that undergo peer review thus providing valuable experience in designing and executing an independent research project. Lastly, student participants gain valuable and diverse skill sets in academic fields essential for national interests. The interactions between and inter-conversion of electrically neutral (exciton) and charged (polaron) states of different spin in conjugated polymer materials has significant bearing on their overall performance in cutting-edge optoelectronic devices, such as solar cells. Although the outcomes of these processes are strongly dependent on polymer structure, detailed molecular level structure-function relationships have proven difficult to obtain from conventional polymer functional forms (i.e., bulk thin films). This difficulty originates from morphological heterogeneity due to intrinsic molecular weight poly-dispersity of polymers. The proposed research seeks to overcome heterogeneity effects to understand how molecular structure regulates interactions and inter-conversion of excitonic and polaronic spin states. Self-assembly approaches are used to fabricate well-defined polymer aggregate supramolecular nanostructures that can be exploited to selectively control conformational and packing (intra- and interchain) order and electronic coupling. The Grey group at the University of New Mexico has pioneered this approach to direct exciton coupling and polaron interactions in polymer aggregates that are leveraged in the proposed research to address longstanding fundamental questions involving spin state exchange interactions and crossover in polymeric semiconductors. This research also takes new directions for interrogating the fates and interactions of different spin states in individual polymer nanostructures by introducing sensitive and selective electric- and magnetic-field dependent molecular spectroscopic and imaging techniques. The research aims to establish design rules for reliably tuning subtle polymer chain packing and order within supramolecular assemblies to understand and control exchange interactions and spin state inter-conversion for improved material performance.