Carboxyethylation of chitosan-based polymeric dyes for potential pH-sensing applications

Background: Polymeric dyes have gained significant attention due to their unique properties and potential applications in various fields. Previous research has shown that chitosan-based polymeric dyes (CSPDs) had excellent color-sensing characteristics, but they had a solubility limitation. Methods: CSPDs were modified by the Michael reaction of acrylic acid in mild conditions. The synthesized derivatives were characterized using various analytical techniques, including FTIR, NMR, and UV-vis. Their crystallinity, thermal properties and solubility were also investigated. Significant findings: The presence of new carboxyethyl groups in novel water-soluble chitosan-based polymeric dyes (WCSPDs) after the modification was confirmed, without affecting their coloring. The derivatives also showed lower crystallinity, making them soluble in water over a wide range of pH values, and exhibited lower thermal stability. Furthermore, the derivatives displayed coloring properties and were nontoxic. These properties suggested the potential use of WCSPDs as sensor materials. In summary, the findings of this study highlighted the potential of WCSPDs as novel polymeric dyes with unique properties that could have significant applications in diverse fields, such as sensing and biomedical engineering.