Linking sprayability to thin-film performance in CNT-redox-polymer dispersions

Carbon nanotube (CNT)-loaded redox-polymer coatings are an attractive class of composite materials for charge storage devices, high-surface area ion-binding platforms, and selective redox mediated separation systems. While CNTs provides a nanoporous conductive network, the electroactivity of the redox-polymers grants these systems high pseudocapacitive charge-storage and ion recognition properties. Metallopolymers in particular are attractive due to their fast electron-transfer, synthetic tunability, and reversibility. However, processing CNT-metallopolymer dispersions to form uniform thin film coatings on large length scales is a substantial challenge. The sprayability, coatability, and printability of these dispersions are dictated by the extensional flow properties. Here, we link the extensional flow properties to the quality of the solution-processed thin film using capillary breakup extensional rheometry (CaBER) to capture filament formation and breakup. The CNT: polymer ratio, polymer molecular weight, polymer chemistry and solvent quality all impact the extensional rheology and corresponding thin film quality. Our results show a strong link between macroscopic flow properties, dispersion processability and final thin-film performance on the electrodes.