Dynamic water vapor sorption behaviour of crosslinked polycationic diallylammonium-based hydrogels

This study explores the water vapor sorption behaviour of polycationic hydrogels based on diallyl ammonium derivatives, with a focus on disentangling how crosslinking density, ionic interactions, and monomer structure govern their thermodynamic and kinetic properties. Five distinct hydrogel formulations were systematically examined using temperature-dependent and isothermal dynamic vapor sorption (DVS) techniques. Thermodynamic analyses revealed positive enthalpy (Δ H = 2.17–4.10 kJ/mol) and entropy (Δ S = 10.7–18.6 J/(mol·K)) values, confirming endothermic sorption processes driven by increased molecular disorder. The activation energy ( E A ) for adsorption ranged from 29.32 kJ/mol to 41.83 kJ/mol, consistent with a hybrid mechanism involving both physical and chemical sorption. The copolymerization with ionic monomers and the incorporation of divalent counterions significantly influenced sorption energetics, where reversible ionic crosslinking enhancing water uptake and tailored desorption pathways. Kinetic analysis indicated diffusion-limited adsorption (Avrami exponents n < 1) and multi-stage desorption dynamics ( n > 1), underscoring the critical roles of steric hindrance and ionic interactions. Diallylpiperidine-based hydrogels exhibited unique directional sorption properties, while highly crosslinked formulations retained structural integrity with reduced swelling. The findings provide practical design guidelines for engineering hydrogels for industrial and environmental applications, including humidity control, moisture barriers, and sustainable advanced material. These results highlight the versatility of polycationic hydrogels as tuneable materials platform that bridges fundamental research and practical applications. • Design rules for humidity control hydrogels from cationic diallylammonium networks. • Detailed analysis of the swelling behaviour • In-depth kinetic and thermodynamic characterization of sorption behaviour