Structure–property–performance relationships in dextran/halloysite nanocomposite hydrogel platforms with tuneable swelling properties for enhanced aqueous remediation

Abstract Dextran-based hydrogels have attracted increasing attention as sustainable polymeric materials owing to their biocompatibility, biodegradability and high affinity for water. In this study, dextran hydrogels with different crosslinking densities were synthesized via epichlorohydrin-mediated crosslinking and reinforced with halloysite nanotubes (HNTs) to obtain nanocomposite hydrogel systems. The combined effects of crosslinking density and HNT incorporation on structural, morphological, porous, swelling, diffusion and methylene blue adsorption properties were systematically investigated. Attenuated total reflectance Fourier-transform infrared (ATR-FTIR) analysis confirmed the formation of crosslinked dextran networks and the incorporation of HNTs, while scanning electron microscopy (SEM) observations revealed increased surface roughness and morphological heterogeneity upon HNT addition. Nitrogen adsorption–desorption analysis showed that the Brunauer–Emmett–Teller (BET) surface area values of HNT, 2DEX-HNT and 4DEX-HNT were highly comparable, whereas differences in pore-size and pore-volume parameters indicated changes in pore accessibility and network compactness. Swelling studies demonstrated that lower crosslinking density resulted in higher water uptake, while diffusion analysis showed that all hydrogel formulations followed Fickian diffusion behaviour. Methylene blue adsorption experiments revealed that HNT-containing hydrogels exhibited higher adsorption performance than non-filled systems, with 4DEX-HNT showing the highest adsorbed dye amount. The increased adsorption behaviour was associated with the combined effects of HNT-derived interaction sites, nanotubular confinement, pore architecture and crosslinked network structure. Overall, this study establishes structure–property–performance relationships in dextran/HNT nanocomposite hydrogels and highlights their potential as tuneable materials for dye adsorption and remediation of aquatic ecosystems.