Structure–Property Relationships of PAM/CMC-Based Semi-IPN Hydrogels: Influence of APS/ANI Ratio on Swelling, Electrical, Thermal, and Morphological Properties

Abstract In this work, semi-interpenetrating network (semi-IPN) hydrogels based on polyacrylamide (PAM)/CMC matrices incorporating polyaniline (PANI) were synthesized to investigate the influence of the ammonium persulfate/aniline (APS/ANI) ratio on structure–property relationships. Hydrogels were prepared via free radical polymerization of PAM/CMC followed by in situ polymerization of aniline within the preformed matrix, yielding composites with systematically varied APS/ANI ratios. Swelling studies in 1.0 mol L–1 HCl revealed that the incorporation of PANI reduced the equilibrium electrolyte swelling degree relative to PAM/CMC hydrogels, yet promoted specific ionic interactions with Cl– ions, strongly dependent on the oxidant/monomer ratio. Electrical conductivity analysis reached values up to 10–2 S·cm–1, with the highest performance observed for hydrogels synthesized at intermediate APS/ANI ratios. Morphological (SEM/EDX) and structural (FTIR, UV–Vis, XRD) analyses demonstrated that PANI formed dendritic-like microstructures distributed within the CMC-containing matrix, while XRD results correlated crystallinity variations with electrical performance. Thermal analysis (TGA) indicated differences in the thermal degradation behavior of the composites compared with the PAM/CMC matrix. These findings highlight the central role of the APS/ANI ratio in modulating the swelling, structural organization, and electroactive properties of PAM/CMC/PANI semi-IPN hydrogels, providing insights for the design of polysaccharide-based conductive materials with potential applications in electroactive devices.