Coupled Ionic-Electronic-Structural Dynamics in Organic Mixed Conductors

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With the support of the Macromolecular, Supramolecular and Nanochemistry program in the Division of Chemistry, Connor G. Bischak of the University of Utah is elucidating the relationship between electronic transport, ion motion, and structural dynamics in conjugated polymers that operate as organic mixed ionic-electronic conductors (OMIECs). OMIECs are soft polymeric semiconductors which can conduct both electronic and ionic charges. This unique ability makes them particularly suitable for a variety of applications of relevance to next-generation bioelectronic, optoelectronic and energy storage devices. However, for many of these applications, it is currently difficult to choose a combination of polymer molecular structure, polymer processing conditions, and electrolyte to achieve a specific performance metric. This project will fill these knowledge gaps by exploiting the high spatial resolution and chemical specificity of novel scanning probe imaging approaches, as well as a complementary suite of traditional and novel in situ techniques. Fundamental correlations established as a result of this work have the potential to help guide synthetic chemists towards synthesizing the next generation of OMIEC conjugated polymers. The interdisciplinary nature of this research will provide strong training and professional development opportunities for high school, undergraduate and graduate students. The project will additionally support an outreach effort to supply local high school chemistry classrooms with affordable 3D-printed spectrometers to learn about light-matter interactions, similar to those that are used to interrogate OMIEC polymers.This research will focus on investigating organic mixed ionic-electronic conductors (OMIECs) to uncover relationships between ion motion, electronic transport, and structural dynamics. Poly(thiophene)s with various backbones comprised of hydrocarbons, oligo (ethylene glycol)s, or carbonyl functionalities will be the focal points, in part because they are currently the highest performing OMIEC materials. In the first specific aim, reversible and irreversible structural dynamics will be investigated using blends of semicrystalline and amorphous polymers to tune the crystallinity and measure ion injection kinetics as a function of crystalline to amorphous polymer ratios. The second aim will extend studies to ion dependent effects. Finally, the impacts of heterogeneous polymer structure will be addressed through correlative nanoscale imaging that will be used to answer basic questions about the doping process and structural dynamics. The combined efforts have the potential to afford new insights into chemical design elements that enable more effective conductivity. This research aims to address critical knowledge gaps in the field with the goal of enabling design of optimal ionic and electronic conductivity in such systems.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.