Influence of sulfonation degree and deposition technique on the electrical and morphological properties of sulfonated polystyrene thin films

Abstract

In this work, sulfonated polystyrene thin films with different sulfonation degrees (3% and 6%) were prepared using Langmuir–Schaefer (LS) and drop‐casting deposition techniques to investigate the influence of chemical functionalization and film fabrication method on their morphological and electrical properties. The Langmuir films were characterized through surface pressure–area isotherms, revealing that increasing sulfonation affects the interfacial organization and molecular packing of the polymer chains. The deposited thin films were further analyzed regarding their surface morphology, conductivity and dynamic electrical response under ammonia exposure. The results demonstrate that both the sulfonation degree and deposition technique strongly influence charge transport behavior and ionic conduction pathways within the films. LS films exhibited higher molecular organization and improved baseline conductivity, whereas drop‐cast films presented more heterogeneous morphologies, favoring larger current modulation and enhanced electrical stability under chemical exposure. In addition, higher sulfonation levels promoted greater ionic interaction and more reproducible electrical responses, particularly for the drop‐cast films. These findings provide important insights into the relationship between processing, molecular organization and electrical properties in sulfonated polymer thin films, highlighting their potential for electrically responsive and chemically interactive thin‐film applications. © 2026 The Author(s). Polymer International published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.