Stretchable current collectors based on carbon embedded in a poly (acrylamide)/poly (N,N-methylenebisacrylamide) hydrogel modified with Nafion 117®

Abstract

In this study, we optimized the dispersion of hydrophobic carbons within ionically conductive hydrogels composed of a poly (acrylamide)-pAAm/poly (N,N-methylenebisacrylamide)-pMBAA modified with Nafion 117 ®. The carbon-embedded hydrogel films were prepared by in situ UV polymerization of aqueous suspension containing KCl, acrylamide and N,Nmethylenebisacrylamide monomers, the multi-walled-carbon nanotubes, graphene, single-walled carbon nanohorns, and their composites with polypyrrole. These electrodes were translucent, stretchable, ionically and electronically conductive at low carbon content. In addition, they were very flexible, reaching a stretch up to 1475.57% of their initial length. Mechanical characteristics and conductivity were measured at their maximum hydration, corresponding to water uptake of 47.20% after 5 days of curing in humidity chamber. Hydrogels with dispersed carbon demonstrated both ionic and electronic conductivity in hydrated state and electronic conductivity alone when the electrode was dry. Nafion 117 ® acted as a surfactant and played a significant role in the improvement of carbon distribution within the hydrogel due to the hydrophobic-hydrophilic interaction between hydrogel, Nafion and the carbon. This was further correlated with changes in zeta potential at the carbon-hydrogel interface upon addition of Nafion, measured using a rotating disk electrode voltammetry.

Flexible Electrode Based on MWCNT Embedded in a Cross-Linked Acrylamide/Alginate Blend: Conductivity vs. Stretching

“…This demonstrates that the hydrogel does not suppress MWCNT conductivity. The hydrogel matrix shows conductivity similar to liquid electrolyte and the MWCNT response is similar to what is typically observed in the liquid electrolyte with a similar KCl concentration [31]. All films showed no influence of twisting at about 180 degrees on the specific conductivity ( Figure 6C,D).…”

“…The hydrogel matrix proposed in this work is formed via copolymerization of acrylamide and bis-acrylamide, with the optimal composition decided based on work reported by Sun et al [22], and by a previous study carried out in our group [31]. Briefly, the reaction is vinyl addition polymerization via a free radical-generating system initiated by ammonium persulfate and TEMED.…”

“…Using surfactants for MWCNT dispersion in the solution of monomers is more challenging, affects the rate of polymerization, and ultimately the chemical composition of hydrogels, their mechanical strength, and conductivity. As compared to our previous study [31], Nafion, acting as a surfactant in an aqueous suspension of MWCNT, has been replaced with the viscous solution of sodium alginate. The alginate can both participate in the cross-linking and stabilize the MWCNT in water.…”

“…In addition, they are excellent double-layer capacitors that cannot be outperformed by more affordable carbons. Thus, CNTs are of interest in energy harvesting and reposition applications [28,31].…”