In the goal of designing polymer systems for electrochemical devices with effective mixed conduction of ions and electrons, it is necessary to understand the requirements for effective transport of both ionic and electronic charge carrier species and to design materials and systems capable of accommodating them. In this dissertation, approaches to probing charge transport in redox active polymeric systems are detailed, and several investigations are highlighted showcasing the characterization and varied application of these systems. In Chapter 2, attention is drawn to several fundamental techniques for probing redox activity and charge transport in electrochemical systems. In Chapter 3, the design and construction of several custom-fabricated instruments for the fabrication and characterization of conductive polymer systems is discussed, allowing those who follow to a means to use, reproduce, and improve upon their design in the future. Chapter 4 highlights an in-depth study of evolving mixed conduction in a conjugated polyelectrolyte, poly[3-(potassium-n-alkanoate) thiophene-2,5-diyl] (P3KnT), in response to an environmental stimulus, ambient humidity. Spectroscopic and morphological analyses reveal the presence of water results in a self-doping phenomenon, but also disturbs molecular packing, resulting in a non-monotonic electronic conductivity profile. This behavior occurs alongside increasing ionic conductivity with a similar overall magnitude. The identification and characterization of a MIEC with mixed conductivity values approaching parity presents an exciting material for electrochemical devices, but also an important model material for studying the tuning of mixed conductivity in such systems. Chapters 5, 6, and 7 discuss the design, synthesis, and implementation of disulfide-bearing insoluble polymer particles for use as rechargeable battery cathodes. Chapter 5 highlights the design of poly(glycidyl methacrylate) (PGMA) particles densely crosslinked with bis(5-amino-l,3,4-thiadiazol-2-yl) disulfide, resulting in redox-active particles with improved electrochemical kinetics when compared to solutions of analogous small molecule disulfides. Implementation of these particles in cathodes reveals stable cycling, but ultimately poor discharge capacity. Chapter 6 showcases a multi-directional approach to improving this performance, modifying particle size, secondary pendant chemistry, and electrode preparation, ultimately showing a dramatically improved cathode capacity without modification of the disulfide redox center. Finally, Chapter 7 highlights preliminary work in designing a disulfide particle system with enhanced intraparticle kinetics, taking advantage of an electrocatalytic effect observed between poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive conjugated polymer, and 2,5-dimercapto-1,3,4-thiadiazole (DMcT), another thiadiazole-derived organosulfur molecule, resulting in discharge capacity at faster charge rates than similarly-sized PGMA counterparts. Chapter 8 demonstrates an alternative use for the disulfide-crosslinked particles in the context of improving performance lifetime for redox flow batteries based on insoluble polymer electrolyte suspensions. Through either electrochemical reduction or UV photoexcitation, particle disulfide crosslinks are cleaved. When these particles are adhered to an electrode surface, this controlled de-crosslinking allows the particles to be washed away from the electrode, increasing its access to the fluid electrolyte and improving flow battery performance without need for disassembly, offering a potential method of in-line regeneration for fouled polymer-based redox flow batteries. A conclusion chapter summarizes the results of these studies and discusses the outlook of polymeric materials for use in energy conversion and storage applications.