SAXS study of electric field-induced microstructural evolution in a polyaniline-based conductive hydrogel

The behavior of conductive polymer networks under applied electric field plays a critical role in the electro-driven drug release of conductive hydrogels. This study investigates a novel conductive hydrogel composed of quaternized chitosan grafted with polyaniline (QCSPA) crosslinked with polyvinyl alcohol (PVA) and borate (BA), focusing on its structural evolution under varying electric fields. Small-angle X-ray scattering (SAXS), analyzed with the correlation length model and Gaussian spherical domain (GSD) fitting, was used to quantitatively characterize the multiscale structure of the hydrogel network. Under natural swelling, the spacing between network chains gradually increased, accompanied by a slow expansion of domain radius and correlation length, while maintaining a surface fractal, random coil-like structure. At 3 V, electric field-induced chain aggregation and swelling-driven expansion resulted in an initial slight contraction of domains followed by gradual expansion, reflecting a transition from mass to surface fractal behavior. Under a 5 V high electric field, chain aggregation intensified, leading to rapid formation of larger, denser domains and an accelerated shift to surface fractal structures. The aggregation and densification of spherical domains reduced the correlation length and accelerated polymer chain breakage and network erosion. Consequently, electric field stimulation drives a transformation of the hydrogel network from a microscopically disordered, loose state to an ordered, more densely packed multiscale structure, accompanied by accelerated macroscopic degradation and a significant reduction in mechanical performance.