Aromatic Pendant Containing Conjugated Polydiacetylene Based Low‐Temperature Irreversible Thermochromic Indicator: Smart Monitoring of Milk Storage

Abstract The remarkable adaptability of chromogenic phases found in polymers like conjugated polydiacetylene (PDA) is especially noteworthy due to their vital role in durable sensing applications. This study presents the synthesis and utilization of polymers and PDA‐based functionalized dyes as a visual color indicator. These dyes are developed by modifying the head groups of 10,12‐tricosadiynoic acid (TC) with aromatic alcohols, employing Steglich esterification. Confirmation of the functionalized dye derivative is achieved using various analytical techniques. In addition, the composite film is fabricated by mixing a modified monomer dye with the polymer polyvinyl alcohol (PVA). The composite film is exposed to UV radiation for topochemical polymerization in order to form PDA. Moreover, the functionalized dyes demonstrate an irreversible color transition (above 10 °C) in thermochromic investigations. The present study revealed that these conjugated PDA‐based thermochromic composite films showcased an irreversible color at low temperatures, which can serve as warning indicators for low‐temperature sensitive milk packets. Any change in the indicator's color by means of storage conditions may help the retailers and end‐users to accept the packet further.