Polymer Composite Hydrogel Based on Polyvinyl Alcohol/Polyacrylamide/Polybenzoxazine Carbon for Use in Flexible Supercapacitors

Polymer gels are cross-linked polymer networks swollen by a solvent. These cross-linked networks are interconnected to produce a three-dimensional molecular framework. It is this cross-linked network that provides solidity to the gel and helps to hold the solvent in place. The present work deals with the fabrication of polybenzoxazine carbon (PBzC)-based gels that could function as a solid electrode in flexible supercapacitors (SCs). With the advantage of molecular design flexibility, polybenzoxazine-based carbon containing different hetero-atoms was synthesized. A preliminary analysis of PBzC including XRD, Raman, XPS, and SEM confirmed the presence of hetero-atoms with varying pore structures. These PBz-carbons, upon reaction with polyvinyl alcohol (PVA) and acrylamide (AAm), produced a composite polymer hydrogel, PVA/poly (AAm)/PBzC. The performance of the synthesized hydrogel was analyzed using a three-electrode system. PVA/poly (AAm)/PBzC represented the working electrode. The inclusion of PBzC within the PVA/poly (AAm) matrix was evaluated by cyclic voltammetry and galvanostatic charge/discharge measurements. A substantial increase in the CV area and a longer charge/discharge time signified the importance of PBzC inclusion. The PVA/poly (AAm)/PBzC electrode exhibited larger specific capacitance (C_s) of 210 F g⁻¹ at a current density of 0.5 A g⁻¹ when compared with the PVA/poly (AAm) electrode [Cs = 92 F g⁻¹]. These improvements suggest that the synthesized composite hydrogel can be used in flexible supercapacitors requiring light weight and wearability.