Hierarchically structured conducting polymer hydrogels with enhanced stretchability and conductivity via freeze-casting and salting-out with oxidant salts

Abstract

High strength, toughness, and conductivity are essential for advanced flexible electronics and bioelectronic materials. However, current approaches to fabricating hydrogels using conductive polymers struggle to achieve the desired mechanical properties, conductivity, and ease of fabrication. This paper proposes a strategy that combines the use of a unique salt with both oxidizing and salting-out capabilities and directional freezing to polymerize poly(3,4-ethylenedioxythiophene) within a poly(vinyl alcohol) hydrogel matrix, creating a robust hierarchical structure. This simple yet effective method produces poly(3,4-ethylenedioxythiophene)-based hydrogels with excellent mechanical and electrical properties. Namely, these hydrogels exhibit an elongation rate of 855 ± 96% and a conductivity of (2.60 ± 0.55) × 10⁻² S cm⁻¹ after polymerization. Moreover, the material demonstrates remarkable electrical properties, maintaining minimal resistance changes and even enhancing conductivity under mechanical stress. The approach outlined in this study yields conducting polymer hydrogels that simultaneously exhibit mechanical strength and conductivity and are easy to fabricate. Therefore, this material is promising for a wide range of applications in flexible electronics and biomedical sensing.