CAREER: Morphology and Property Correlations of Chemically Doped 1D Conjugated Polymer Aggregates

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This project is jointly funded by the Polymers Program in the Division of Materials Research and the Experimental Program to Stimulate Competitive Research (EPSCoR).NON-TECHNICAL SUMMARY:The research objective of this CAREER project is to gain fundamental knowledge of the correlation between morphology at the nanoscale and optoelectronic properties of chemically doped one-dimensional conducting polymer aggregates. The planned research and educational activities have broad impacts by tackling current national needs in both materials and human workforce development. The knowledge gained in the project will promote rational design of more efficient organic materials for electronic applications, as well as more efficient processing and fabrication techniques for future organic electronic devices. With the current world organic electronics market size expected to grow significantly in the next decade, enhancements on just a fraction of the organic electronic materials could have an impact on US and global economy. This program also provides a platform for participating students to gain expertise from interdisciplinary fields including materials science, chemistry, and surface science. Hands-on activities involving polymer science and nanoscience will be offered to K-8 students for early exposure to scientific topics. High-school polymer nanoscience workshops will provide students hands-on experience on preparing and characterizing functional nanostructures. Extra efforts will be devoted to recruiting and involving underrepresented and economically disadvantaged K-12, undergraduate, and graduate students into these outreach activities. Successful execution of these integrated research and education activities will enhance diversity in US scientific research and inspire more K-12 and undergraduate students to pursue STEM careers.TECHNICAL SUMMARY:The systematic local morphology-property correlation of non-doped and doped 1D conjugated polymer aggregates gained by AFM-based methods is the primary goal of this project. To achieve this goal, monolayer and multi-layer conjugated polymer nanowhiskers are chosen as the model systems in this program because most of the polymer molecules within monolayer nanowhiskers are surface molecules that can be directly investigated by surface characterization tools. Multi-layer nanowhiskers will be subsequently studied in a "layer-by-layer" manner on the basis of what was learned from monolayer nanowhiskers. Local morphology-property relationship for doped and non-doped conjugated polymer nanowhiskers will be analyzed using AFM and its advanced modes. The doping reaction in solution will be systematically studied by UV-vis spectroscopy to reveal the influences of many parameters, particularly the aggregation forms, on the chemical doping reaction kinetics. The charge transport in and between 1D conjugated polymer aggregates will also be interrogated at nanometer scale. This program is expected to reveal structure and property fluctuations at nano- to micrometer scales that are otherwise hidden in ensemble measurements. The conductivity studies within and between nanowhiskers will elucidate the interrelated roles of defect sites, ordered/disordered domains, connection points, and chemical doping on the charge transport of conjugated polymer materials. The results of the chemical doping reaction kinetic dependence on the reaction conditions, especially conjugate polymer microscopic aggregation forms, will supply practical solution-based applications with crucial macroscopic doping reaction kinetics information that is largely missing so far. The comprehensive understanding of the chemical doping of conjugated polymers accumulated in this program will enable researchers in this field to seek suitable strategies based on concrete organic doping knowledge rather than through empirical trials.