Evaluation of the Water Absorption Capacity of Sulphonated Polystyrene Films Prepared in Different <scp>pH</scp> Environment

ABSTRACT Polystyrene (PS)–based polymer films are widely used in coatings and packaging; however, their low surface wettability and limited interaction with aqueous environments restrict their application in functional materials. Chemical modification through sulfonation is an effective approach to tailor the surface and water interaction properties of PS. In this study, sulfonated polystyrene (SPS) with a sulfonation degree of 10% was synthesized and used to prepare polymer films with varying SPS contents, with and without a plasticizer. The films were characterized in terms of chemical structure, surface morphology, thermal stability, wettability, and water absorption behavior. FTIR spectroscopy confirmed the successful introduction of sulfonic acid (–SO 3 H) groups, while SEM analysis revealed morphological changes due to SPS incorporation, including microstructural features arising from interactions between ionic (SPS) and nonionic (PS) components. Thermogravimetric analysis showed that all films retained satisfactory thermal stability, with degradation behavior influenced by SPS content and plasticizer addition. Surface wettability and long‐term water absorption were evaluated under acidic, neutral, and alkaline conditions for up to 30 days. The results indicate that SPS content and plasticizer addition significantly affect the hydrophilic–hydrophobic balance of the films, with water absorption increasing with SPS content and plasticized films generally exhibiting reduced water uptake.