## 3 Results and Discussion
### Study of the Photo-Oxidation Kinetics of AHMPD with Polymers P2, P3, and P4 as Photosensitizers
For this purpose, the model reaction of anthracene-9,10-dipropionic acid photo-oxidation to form ADPA-O\({}_{2}\) endoperoxide, which is widely studied in aqueous media, was performed (1.2 \(\times\) 10\({}^{-4}\) M in Milli-Q water). This reaction was previously utilized for the same polymers in the prior work [19], and it has long been used as a control [42]. The results obtained are also presented in Table 2 and are consistent with those reported in the previous study. Table 2 presents the relative effectiveness of polymers P1-P4 in both reaction media with different pH. The reaction at pH = 11 is more efficient because the photo-oxidation mechanism is favored in an alkaline environment, as will be explained later. The differences in the photooxidative capacity of polymers P2-P4 are attributed to the varying hydrophilic properties of each structure, with more favorable results in the more hydrophilic polymers, P3 and P4, respectively. The introduction of the functional group \(\gamma\)-gluconolactone, in addition to ethylenediamine, provides greater hydrophilicity and increases the reaction efficiency by approximately 10% for AHMPD in both media (pH = 7 and pH = 11) for P4. However, in experiments that evaluate the singlet oxygen generation capacity for the photo-oxidation of ADPA, both P3 and P4 exhibit similar capacities. Finally, it is worth mentioning that in all cases, both controls--the P1 polymer (without RB) and the experiments conducted in the dark--did not result in any photo-oxidation reactions. Additionally, no leaching was observed in any of the polymers and recyclability experiments of polymers P3 and P4 showed no loss of photocatalytic capacity over five reaction cycles. Interpretation of the Photocatalytic Mechanism for the Photo-Oxidation of AHMPD Using Rose of Bengal  
According to the literature, the photo-oxidation reaction of AHMPD-type pyrimidines through sensitization can be summarized as follows. The first step is the excitation of the photosensitizer (Figure 5a). When Rose Bengal absorbs visible light (500-600 nm), it transitions from its ground state (RB or Sens) to an excited singlet state (RB* or Sens*), and singlet oxygen (O\({}_{2}\)(\({}^{1}\Delta_{\text{g}}\))) is generated from the ground state molecular oxygen (O\({}_{2}\)(\({}^{3}\Sigma_{\text{g}}\))). Next, the oxidation of AHMPD occurs to form a zwitterionic compound that can be identified as AHMPD+O\({}_{2}\) (Figure 5b), formerly proposed by [PERSON] and [PERSON] [43] and corroborated by [PERSON] [36]. In this work, we have not analyzed the products of the sensitized photo-oxidation of AHMPD and rely on the mechanisms described in the literature. However, it \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{3}{*}{**Polymer**} & \multicolumn{2}{c}{**Photo-Oxidation Reaction of**} & \multicolumn{2}{c}{**Photo-Oxidation Reaction of**} & \multicolumn{2}{c}{**Quantum Yield in Singlet Oxygen**} \\  & \multicolumn{2}{c}{**AHMPD at pH = 11**} & \multicolumn{2}{c}{**AHMPD at pH = 7**} & \multicolumn{2}{c}{**Generation Measured with ADPA Reaction**} \\ \cline{2-8}  & \multirow{2}{*}{**Maximum**} & \multirow{2}{*}{**Normalized**} & \multirow{2}{*}{**Maximum**} & \multirow{2}{*}{**Normalized**} & \multirow{2}{*}{**Maximum**} & \multirow{2}{*}{**Normalized**} & \multirow{2}{*}{**Relative**} & \multirow{2}{*}{**\(k_{obs}\)**} \\  & & & & & & & & \\ \cline{2-8}  & \multirow{2}{*}{**Maximum**} & \multirow{2}{*}{**Relative**} & \multirow{2}{*}{**Conversion**} & \multirow{2}{*}{**Effectiveness**} & \multirow{2}{*}{**Conversion**} & \multirow{2}{*}{**Effectiveness**} & \multirow{2}{*}{**Relative**} & \multirow{2}{*}{**(10\({}^{-4}\) min\({}^{-1}\))**} \\  & & & & & & & & \\ \hline Darkness & 0\% & - & 0\% & - & 0\% & - & - \\ P1 & 0\% & - & 0\% & - & 0\% & - & - \\ P2 & 64\% & 0.75 & 3\% & 0.23 & 85\% & 0.85 & 432 \\ P3 & 76\% & 0.89 & 12\% & 0.92 & \(>\)99\% & 1.00 & 635 \\ P4 & 84\% & 1.00 & 13\% & 1.00 & \(>\)99\% & 1.00 & 640 \\ \hline \hline \end{tabular}
\end{table}