*3.4. Differential Thermal Analysis (DTA) and Thermogravimetric Analysis (TGA)*

The pure chitosan TGA curve has two stages of thermal degradation (Figures 4 and 5). The first stage is associated with a small weight loss due to the evaporation of the adsorbed and weakly bound water (mass loss 7%, Tmax = 121 ◦C). This stage is accompanied by a weak endothermic effect. The second stage is associated with the degradation of the polymer structure (mass loss 89%, Tmax = 520 ◦C).

**Figure 3.** XRD patterns of chitosan and POX-1 (**A**); XRD patterns of chitosan and deferoxamine (**B**); XRD patterns of POX-1, POX-2 and deferoxamine (**C**); XRD patterns of POX-2 and POX-3 (**D**).

**Figure 4.** TGA curves of DESF, CH, POX-1, POX-2, POX-3.

**Figure 5.** DTA curves of DESF, CH, POX-1, POX-2, POX-3.

POX-1 was obtained by the interaction of chitosan with Fe3+ ions. The thermal degradation curve of POX-1 is characterized by three stages of degradation. The first stage is associated with water loss, and it is accompanied by a slight endothermic effect (mass loss 10%, Tmax = 122 ◦C). The second stage is associated with the degradation of the polymer structure, and it is accompanied by a pronounced, unsharp exothermic effect (mass loss 73%, Tmax = 440 ◦C). The third stage of decomposition has a spasmodic, pronounced exothermic effect (mass loss 10%, Tmax = 453 ◦C) (Figures 4 and 5).

POX-2 and POX-3 were prepared via the interaction of POX-1 with deferoxamine. Their thermal decomposition curves are almost identical, and the values of weight loss and maximum temperature differ by no more than 10% (Figures 4 and 5). The first stage of thermal degradation is associated with water loss (mass loss 7%, Tmax = 146 ◦C). The second stage is accompanied by an acute exothermic effect (mass loss 25%, Tmax = 200 ◦C) followed by a gradual loss of mass. The third stage is accompanied by a sharp, pronounced exothermic effect (Tmax = 445 ◦C, weight loss 20%). The POX-1 and POX-2 curves are significantly different from those of the starting deferoxamine and POX-1, which indicates the formation of new systems. The systems include the characteristic features of the thermal decomposition of both starting deferoxamine and POX-1: (i) deferoxamine-like weight loss at 200 ◦C (for deferoxamine, at 202 ◦C); (ii) POX-1-like sharp weight loss at 445 ◦C (for POX-1, at 453 ◦C). These observations are in agreement with the results of the X-ray diffraction study.
