Dual‐Crosslinked Sodium Alginate/Gelatin Hydrogel Microspheres With <scp>pH</scp> ‐ and Temperature‐Responsive Swelling Behavior

ABSTRACT Sodium alginate/gelatin (SA/GE) composite hydrogel microspheres were prepared via a combined ionic and chemical crosslinking strategy using calcium ions and glutaraldehyde as crosslinkers. The formation of an interconnected polymer network with well‐defined spherical morphology was characterized. The environmental responsiveness of the composite hydrogels was systematically investigated by examining their swelling behavior under different pH conditions (pH 5, 7.4, and 9) and temperatures (25°C–40°C). The swelling kinetics were further analyzed using pseudo‐first‐order and pseudo‐second‐order kinetic models to quantitatively describe the swelling process. The results demonstrate that the swelling behavior is strongly dependent on environmental pH and temperature. The response is governed by pH‐dependent charge regulation within the dual polyelectrolyte network, arising from the combined ionization of alginate carboxyl groups and gelatin amino groups, together with temperature‐dependent network interactions. Among the investigated formulations, the hydrogel with a SA‐to‐GE mass ratio of 2:2 exhibited a favorable balance between swelling responsiveness and structural stability. In addition, the hydrogel demonstrated good reversibility under cyclic pH and temperature stimuli. The findings indicate that SA/GE composite hydrogels possess controllable swelling behavior and well‐defined swelling kinetics, thus highlighting their potential as stimuli‐responsive polymeric materials for aqueous and environmentally responsive applications.