Polyelectrolyte Complex Gelation of Nafion as a Polymer Binder for Carbon Composites and Its Implications for...

Polymer binders play a critical role in determining the mesoscale organization of particulate composites, yet their physical state during composite fabrication is rarely considered as a tunable parameter. In this study, we investigate the formation of a gel-state polymer binder through polyion complex (PIC) formation between the polyanionic polymer Nafion and the polycation poly(diallyldimethylammonium chloride). The resulting PIC system forms a hydrogel network without altering the chemical structure of the constituent polymers. Rheological measurements confirm the gel-like character of the resulting material, and scanning electron microscopy of the dried gels reveals fibrous film-like structures indicative of polymer network formation. When incorporated as a binder in carbon composite electrodes for electric double-layer capacitors (EDLCs), the gel-state system maintains electrochemical performance comparable to that of conventional Nafion binders. Microstructural observations of the binder and slurry surfaces show relatively uniform distributions of activated carbon and carbon black, consistent with effective particle dispersion within the composite. These results suggest that polyion complex gelation can modify the physical state of polymer binders and influence particle organization during composite fabrication. The study highlights the role of gel-state polymer binders in controlling composite microstructure and provides insight into polymer network-mediated assembly in electrochemical composite materials.