Flexible Composite Hydrogels Based on Polybenzoxazine for Supercapacitor Applications.

Area of Science:

• Polymer Science
• Materials Science
• Electrochemistry

Background:

• Polybenzoxazines (Pbzs) are advanced phenolic resins with excellent thermal stability and self-curing properties.
• However, polybenzoxazines exhibit inherent brittleness, limiting their applications.
• Polyvinyl alcohol (PVA) is a water-soluble synthetic polymer known for its film-forming ability and flexibility.

Purpose of the Study:

• To reduce the brittleness of polybenzoxazines (Pbz) by blending them with polyvinyl alcohol (PVA).
• To synthesize and characterize novel PVA/Pbz composite films.
• To evaluate the potential of these composite films as flexible electrolytes for supercapacitor applications.

Main Methods:

• Synthesis of benzoxazine monomer (Eu-Ed-Bzo) via Mannich condensation.
• Preparation of PVA/Pbz composite films with varying Pbz content (1, 3, 5 wt. %).
• Characterization using FT-IR, NMR, DSC, TGA, SEM, and water contact angle analysis (WCA).
• Evaluation of swelling properties and supercapacitor performance (AC//PVA/Pbz5//AC).

Main Results:

• Successful synthesis and characterization of the benzoxazine monomer and PVA/Pbz composites.
• PVA/Pbz composites showed a transformation from hydrophobic to hydrophilic nature (WCA of PVA/Pbz5 is 35.5°).
• The composite films exhibited suitable swelling properties for electrolyte applications.
• A symmetric supercapacitor constructed with PVA/Pbz5 gel achieved a specific capacitance of 170 F g⁻¹.

Conclusions:

• Blending polybenzoxazines with polyvinyl alcohol effectively reduces brittleness, creating flexible composite films.
• These PVA/Pbz composite films demonstrate tunable hydrophilicity and good swelling characteristics.
• The developed composite films show promise as flexible electrolytes for high-performance supercapacitors.