Thermochromic PDA/ZnO Nanocomposites in PVA for Colorimetric Temperature Sensors

ABSTRACT In this study, thermochromic nanocomposite films based on poly(vinyl alcohol) (PVA), 10,12‐pentacosadiynoic acid (PCDA), 10,12‐tricosadiynoic acid (TCDA), and zinc oxide (ZnO) were synthesized via UV‐induced polymerization and characterized for their thermal, optical, and surface properties. SEM analysis revealed lamellar structures with good dispersion of ZnO, while UV–vis spectroscopy confirmed the typical phase transitions of polydiacetylenes. Thermal analysis showed decomposition between 200°C and 450°C, with PDA‐based films displaying slightly higher thermal stability. The films showed color changes as a function of temperature, occurring at 140°C for PCDA and 180°C for TCDA, demonstrating the influence of the chemical structure on thermal stability and thermochromic response. Contact angle measurements indicated hydrophilic surfaces (70°–80°). Despite promising performance, UV aging tests revealed limited photo‐stability. These results demonstrate the potential of PDA.ZnO.PVA films for thermochromic sensing applications and highlight the influence of diacetylene structure on thermal and optical behavior.