Synthesis and color properties of novel polymeric dyes based on grafting of anthraquinone derivatives onto O-carboxymethyl chitosan

Abstract

Four polymeric dyes were prepared by grafting brominated anthraquinone derivatives onto O-carboxymethyl chitosan through Ullmann condensation. The chemical structure of the prepared polymeric dyes was determined by Fourier transform infrared spectroscopy (FT-IR), elemental analysis and differential scanning calorimetry (DSC), and the results showed that the anthraquinone derivatives were successfully grafted onto O-carboxymethyl chitosan. The grafting degrees of the four polymeric dyes were 0.66, 1.14, 0.93 and 1.01 mmol g⁻¹ respectively. The color performance of brominated anthraquinone derivatives and prepared polymeric dyes was determined and compared using digital photographs and UV-Vis adsorption spectra, and it was found that the electronic properties and planarity of the substituent group in the anthraquinone derivatives obviously affected the adsorption wavelength of the prepared polymeric dyes. In addition, the polymeric dyes with an electron donating group and higher planarity showed longer adsorption wavelengths and more deep color. The cytotoxicity of prepared polymeric dyes was tested, and their IC₅₀ values on human liver cell lines LO2 were 7.666, 8.557, 8.186 and 8.934 g L⁻¹ respectively, suggesting low cytotoxicity of the prepared polymeric dyes.