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Author: search.filters.author.Chalitangkoon, JongjitSubject: search.filters.subject.Chitosan

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    Synthesis of chitosan-based polymeric dyes as colorimetric pH-sensing materials: Potential for food and biomedical applications
    (2021-05-15)
    Chalitangkoon, Jongjit
    ;
    Monvisade, Pathavuth
    pH-sensitive polymeric dyes were fabricated by grafting phenol red (PR) and rosolic acid (RA) onto chitosan (CS) by a facile method. Successful grafting was confirmed by <sup>1</sup>H NMR, FT-IR, UV–vis, XRD, and elemental analysis. The polymeric dyes exhibited no cell toxicity. The colorimetric pH-sensing films were fabricated by blending the polymeric dyes with CS to establish their pH-dependent color properties. The film color changed in the pH range 4–10, which may indicate food spoilage or wound status. Covalently grafting of polymeric dyes in the films led to excellent color stability, leaching resistance, and reversibility. Hence, the synthesized polymeric dyes had potential as pH-indicative colorants for food and biomedical fields.
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    Dual pH/thermal-dependent coloring polymeric dye through Mannich reaction of chitosan: Synthesis and characterization
    (2019-11-01)
    Chalitangkoon, Jongjit
    ;
    Monvisade, Pathavuth
    A novel polymeric dye was synthesized by one-pot Mannich reaction of chitosan (CS) and phenolphthalein (PHP). The grafting onto side chain of CS derivatives was confirmed by UV–vis, FT-IR, <sup>1</sup>H NMR techniques. The degree of substitution (DS) calculated by <sup>1</sup>H NMR and elemental analysis was revealed to increase with increasing mole ratio of formaldehyde and PHP. XRD analysis showed that the grafting through Mannich reaction was caused to amorphous structure in the derivatives. Covalent grafting of PHP onto CS made the grafted products showing pink color in basic conditions without leaching of dye and color fading after several weeks. Moreover, the derivatives dissolved in LiOH/urea systems could showed darker pink after heating. The results suggested that the novel CS derivatives with dual pH/thermal-dependent coloring property could potentially be prepared as pH/thermal-responsive biomaterial in a wide range of applications.