## 3 Results and Discussion
### Thermal Analysis in Air  
In order to achieve the second objective of the work, to assess the effect of copper (II) on the thermal decomposition of examined resins and to identify the solid decomposition products, materials with a homogeneous elementary composition, containing copper atoms (not sodium), were selected for analysis. Eight materials--two starting cation exchangers (M/H, G/H), two cation exchangers in the Cu\({}^{2+}\) form (M/Cu, G/Cu), two cation exchanger in the Cu\({}^{2+}\) form with a CuO deposit (M/Cu#CuO, G/Cu#CuO), and two cation exchanger in the H\({}^{+}\) form with a CuO deposit (M/H#CuO, G/H#CuO)--were subjected to thermal analysis. The results are grouped according to the structure of the polymeric support (macroticular or gel-like) and the medium in which the process proceeded (air or N\({}_{2}\)). TG/DTG curves of sixteen experiments with numerical data characterizing the particular transformation, their temperature range, and the temperature at which the maximum decomposition rate, end temperature, mass change, and residual mass occurred are presented. These findings give an opportunity to analyze such phenomena as the effect of the ionic form of the carboxylic groups on the water content of the material. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \multirow{2}{*}{**Stage**} & \multicolumn{2}{c}{**Substrate**} & \multicolumn{2}{c}{**Product**} & \multirow{2}{*}{**Mass**} & \multicolumn{2}{c}{**Cu Content in Sample**} & \multirow{2}{*}{**Colour of the Product**} \\ \cline{2-2} \cline{5-8}  & **Code** & & & & & **Mass, g** & & **Growth, \%** & **meq/g** & **mg/g** & **Product** \\ \hline \multicolumn{8}{c}{**Macrocircular cation exchanger as polymeric support**} \\ \hline A, B & M/H & 9.36 & M/Cu & 13.54 & +44.5 & 7.10 & 225.6 & Light blue \\ \hline C & M/Cu & 10.01 & M/Na\#CuO & 11.85 & +18.2 & 5.07 & 161.0 & Dark grey \\ \hline D & M/Na\#CuO & 4.08 & M/Cu\#CuO & 4.26 & +4.4 & 10.30 & 327.3 & Grey blue \\ \hline E & M/Na\#CuO & 4.03 & M/H\#CuO & 3.10 & -23.1 & 6.15 & 195.4 & Grey \\ \hline \multicolumn{8}{c}{**Gel-like cation exchanger as polymeric support**} \\ \hline A, B & G/H & 9.42 & G/Cu & 13.71 & +45.5 & 7.21 & 228.9 & Dark green \\ \hline C & G/Cu & 10.35 & G/Na\#CuO & 12.52 & +20.1 & 5.76 & 182.9 & Black \\ \hline D & G/Na\#CuO & 4.31 & G/Cu\#CuO & 4.49 & +4.17 & 11.16 & 354.4 & Black \\ \hline E & G/Na\#CuO & 4.17 & G/H\#CuO & 3.22 & \(-\)22.8 & 7.35 & 233.3 & Black \\ \hline \end{tabular}
\end{table} 
Table 2: Data of the transformations of carboxylic cation exchangers into HIXs with cupric deposit. Figure 1: Photographs of examined materials based on macroporous carboxylic cation exchanger (left column), solid residues after their thermal analysis in air (middle column) and in N\({}_{2}\) (right column). Figure 2: Photographs of examined materials based on gel-type carboxylic cation exchanger (left column), solid residues after their thermal analysis in air (middle column) and in N\({}_{2}\) (right column). Figure 3a shows the TG/DTG curves recorded in air atmosphere for M/H, in which the existence of four decomposition steps associated with mass losses can be observed. The first decomposition step up to 132.8 \({}^{\circ}\)C (maximum decomposition rate at 78.4 \({}^{\circ}\)C) with a mass loss of 4.0% corresponds to the elimination of osmotic water molecules existing in the pores of resin and hydrogen-bonded water (from hydration sites of carboxylic groups). Compared to the ion exchangers of various type [40; 41; 59; 60], this result is very low and indicates that CCE in the H\({}^{+}\) form is especially weakly hydrated. The second step up to 282.1 \({}^{\circ}\)C (maximum decomposition rate at 237.8 \({}^{\circ}\)C) with a mass loss of 11.1% can be assigned to the water elimination between two neighboring carboxylic groups with the creation of some polyacrylic cyclic anhydrides by intermolecular dehydration (5-atom ring such as succinin anhydride type or 6-atom ring such as glutamic anhydride type, Scheme 2).