Three-dimensional (3D) nanostructured conducting polymer hydrogels represent a group of highperformance electrochemical energy-storage materials. Here, we demonstrate a molecular self-assembly approach toward controlled synthesis of nanostructured polypyrrole (PPy) conducting hydrogels, which was "cross-linked" by a conjugated dopant molecule trypan blue (TB) to form a 3D network with controlled morphology. The protonated TB by ion bonding aligns the free sulfonic acid groups into a certain spatial structure. The sulfonic acid group and the PPy chain are arranged by a self-sorting mechanism to form a PPy nanofiber structure by electrostatic interaction and hydrogen bonding. It is found that PPy hydrogels doped with varying dopant concentrations and changing dopant molecules exhibited controllable morphology and tunable electrochemical properties. In addition, the conjugated TB dopants promoted interchain charge transport, resulting in higher electrical conductivity (3.3 S/ cm) and pseudocapacitance for the TB-doped PPy, compared with PPy synthesized without TB. When used as supercapacitor electrodes, the TB-doped PPy hydrogel reaches maximal specific capacitance of 649 F/g at the current density 1 A/g. The result shows that PPy nanostructured hydrogels can be tuned for potential applications in next-generation energy-storage materials.
Retractable, self‐healing, and conductive hydrogels are widely used as adjustable and wearable sensing materials. Herein, using polyfunctional trypan blue (TB) as a crosslinking agent for both poly(acrylic acid) (PAA) and polypyrrole (PPy), a retractable and self‐healing PAA‐TB‐PPy hydrogel is prepared. The introduction of TB not only improves the water retention capacity of the hydrogel but also helps form a highly interconnected conductive path. It is found that PAA‐TB‐PPy hydrogel shows a high electrical conductivity (15 S m−1) which is almost equivalent to the pure PPy hydrogel. Due to the high stability of the semi‐interpenetrating network structure, the elongation at break of PAA‐TB‐PPy hydrogel is more than 750%, along with high mechanical strength and strong adhesion to a variety of solid surfaces. In addition, the hydrogel exhibits high strain and pressure sensitivity with prominent linearity. Importantly, the as‐prepared hydrogel sensor can reliably detect both repetitive large strain and subtle vibration, which makes it a great candidate as wearable electronics for human motion monitoring.
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