Self-Assembly and Cross-Linking of Conducting Polymers into 3D Hydrogel Electrodes for Supercapacitor Applications

Conducting polymer hydrogels (CPH) have attracted interest for use in electronics, biomedical devices, tissue engineering, drug delivery, and energy storage thanks to their electroactivity along with an outstanding capacity to absorb large amounts of water. They are often made by polymerizing a conducting monomer in the presence of a nonconducting polymer scaffold, which can be detrimental to the electrical conductivity of the resulting polymer hydrogel. In this study, we demonstrate an innovative approach for the synthesis of conducting polymer hydrogels (CPH) without using either additives or cross-linkers, leading to conjugated polymers with enhanced electronic conductivity and large surface areas. The feasibility and versatility of our approach are demonstrated by producing a wide range of CPHs including polyaniline, polypyrrole, and poly(3,4-ethylenedioxythiophene), whose biocompatibility and electronic conductivity offer great potential for use as bioactive scaffolds for tissue regeneration and stimulation. The excellent mechanical properties of CPHs can be attributed to the intermolecular forces generated between conducting polymer chains and/or their environment that maintain the hydrogel structure, acting as self-cross-linkers. Given the outstanding charge storage properties, polyaniline hydrogel was utilized as an active material in redox supercapacitors, which delivered a high gravimetric capacitance of 492 F g(-1) at a current density of 1 A g(-1). We have also demonstrated that polyaniline (PANi) can be used as a cross-linking agent for the preparation of a 3D graphene hydrogel with high volumetric and areal capacitances, enabling supercapacitors with excellent electrochemical performance and long-term cycling stability.