Title: Dopant Transport and Distribution in Semicrystalline Conductive Polymers
Ionically and electronically conducting polymers are unique in their ability to conduct both ions and electrons within a single material system, making them well-suited for applications in sensing, biointerfacing, and energy technologies. However, optimizing ionic and electronic conduction in mixed conducting polymers often involves a trade-off: ionic conductivity tends to be linked to structural disorder, while electronic conductivity benefits from charge delocalization in ordered structures. This dichotomy, coupled with the need for charge neutrality between oppositely charged ionic and electronic species, raises a critical question: how do these disparate properties coexist within semicrystalline conductive polymers? This talk delves into this question through three interrelated narratives. The first focuses on the complexities of introducing charge via chemical doping, employing proton-donating Brønsted acids as molecular dopants. By deconvoluting the contributions of reaction and diffusion, we uncover their contributions in determining overall doping limitations. This approach provides new insights into mechanisms of how Bronsted acids can overcome traditional requirements for energy-level matching between polymers and dopants and limitations in their diffusion. The second narrative shifts to exploring the role of polymer-ion interactions and polymer aggregation on ionic conductivity in semicrystalline polyelectrolytes. By using photoresponsive polyelectrolytes, we manipulate polymer aggregation in-situ. This allows us to control aggregation and demonstrate how polymer-ion interactions influence ionic conductivity, even overcoming conventional design principles linked to polymer structural disorder. The final narrative investigates the distribution of ions in the ordered and disordered domains of semicrystalline conductive polymers at equilibrium. Through resonant soft X-ray scattering and simulation-aided analysis, we examine the chemistry, structure, and orientation of doped semicrystalline conductive polymers, revealing distinctive patterns in dopant distribution and chemical structure. This investigation provides unparalleled insights into the organization of dopants within these materials. Ultimately, this work not only enhances our understanding of dopant transport and distribution but also paves new avenues for the simultaneous optimization of ionic and electronic conduction in semicrystalline conductive polymers.