Synthesis and characterization of azo polymers based on chitosan and acrylamide derivatives

Two azo-containing materials, an acrylamide-derived azo compound (AZO 1) and a chitosan-derived azo material (AZO-chitosan 2), were prepared by diazo coupling with o-cresol under alkaline conditions at 0–5 °C. The acrylamide-derived monomer was subsequently converted to an azo polymer by free-radical photopolymerization under nitrogen using 1-hydroxycyclohexyl phenyl ketone (Irgacure 184) as the photoinitiator. The products were characterized by FTIR, ¹H NMR, and ¹³C NMR spectroscopy, and their thermal behavior was evaluated by TGA and DSC. The acrylamide-derived azo compound was obtained in 78% yield, whereas the AZO-chitosan product was obtained in 70% yield. The spectral changes support formation of the azo-containing products and consumption of the polymerizable double bond. The two polymer samples showed TGA onset temperatures of 110 and 100 °C, 50% mass-loss temperatures of 260 and 270 °C, and residues of 92% and 90% at 600 °C, respectively. DSC gave glass-transition temperatures of 180 and 250 °C. These results establish the structural and preliminary thermal characteristics of the prepared materials. Molecular-weight distribution and photoisomerization were not measured and therefore remain subjects for further study.