pH-Responsive Polymer Films Based on Click Polymerization for Food Freshness Monitoring: Non-Toxic, Non-Leaking, and Antibacterial

With the requirements for food safety and quality, there has been increasing attention on intelligent food packaging, especially pH-responsive intelligent packaging. However, the toxicity of indicators and the vulnerability of composite films to leakage tend to change the composition of food and endanger human health. In this study, 2-allyoxy-1-hydroxy-anthraquinone (AhAQ), a pH-responsive plant dye that was modified from alizarin (AI), was grafted onto the pH-responsive intelligent film (AhAQF) via click polymerization. The obtained AhAQF film shows color change in response to ammonia vapor and exhibits adequate reversibility after treatment with volatile acetic acid. The obtained AhAQF exhibits zero leakage, owing to the covalent immobilization of AhAQ. Thus, the prepared pH-responsive films are non-toxic and antibacterial and show promising application prospects in visual food intelligent packaging and gas-sensitive labels.