Charge-Neutralized Colloids for Waterborne High-Energy Dielectrics

Colloids are attractive building blocks for the assembly of organized functional materials. However, their stabilizing surface charges limit the high voltage tolerance and the capacitive energy storage of resultant solid films, which has long remained challenging for dielectric applications of colloids. Here, we propose a strategy of electrostatically complexing colloids with oppositely charged polyelectrolytes to neutralize their surface charges and achieve waterborne high-energy dielectrics. Polyvinylidene fluoride latex, a reference dielectric polymer, interacts electrostatically with a biosourced polycation, chitosan, to generate hybrid particles with tunable surface charge properties. The presence of chitosan prevents the coalescence of the latex particles, yet drives their assembly to form closely packed heterogeneous films. At the isoelectric point where the dispersion exhibits a zeta potential close to 0, the resulting nanocomposites demonstrate the highest Weibull breakdown strength (630 MV/m) and recoverable energy density (10.1 J/cm3), which are respectively 279% and 421% higher than the coalesced counterpart. The validated principle has been successfully extended to other colloidal systems, such as polystyrene latex and aqueous bentonite suspension, highlighting the versatility of the proposed approach to develop waterborne high-energy dielectric materials.