GREEN SYNTHESIS OF THERMO/PHOTOCHROMIC DOPED CELLULOSE POLYMER: A BIOCOMPATIBLE FILM FOR POTENTIAL APPLICATION IN COLD CHAIN VISUAL TRACKING

To mitigate food losses and ensure a robust cold chain in transportation, sensors play a pivotal role in swiftly and visibly monitoring storage conditions. Molecules with thermo- and photochromic properties and N-salicylideneanilines and derivatives, have emerged as promising candidates due to synthesis simplicity and ability to respond to stimuli. In this study we have synthesized a family of anils through mechanochemistry, focusing on H/F substituents on the bromoaniline residue. A suitable photochromic compound was identified and incorporated into a carboxymethyl cellulose (CMC) biopolymer matrix, to produce a photochromic composite film. UV radiation induced a color change in the film from colorless to red: reversibility was evaluated at different temperatures by means of UV-Vis spectroscopy. The composite film maintained a deep red color at -19 °C and 4 °C for seven weeks, while rapidly reversing to white/yellowish at room temperature, making it suitable for cold chain transport and scenarios requiring rapid visual inspection of storage conditions.