## 3 Results
### Work of Adhesion of Organic Solvents on Modified Copolymer
Furthermore, the comparison between the various modifiers led us to conclude using Figure 3 that the maximum adhesion work was obtained with 5-FU. The enhanced adhesion energy observed in the S-DVB copolymer modified by 5-FU can be attributed to several molecular-level mechanisms involving both surface energy modulation and specific intermolecular interactions, detailed as follows:  
1. Molecular features of 5-fluorouracilacil. 5-FU is a highly polar molecule characterized by multiple hydrogen bond donors and acceptors, particularly from its amide (C=O) and imine (N-H) groups. The presence of a fluorine atom with strong electronegativity contributed to dipole-dipole interactions and localized electron density. These features enable 5-FU to interact strongly with both the polymer backbone and the adsorbing solvents. 2. Surface energy regulation by 5-FU. The incorporation of 5-FU onto the S-DVB surface increases the polar component of the surface energy \(\gamma_{s}^{p}\) through hydrogen bonding and dipole interactions. The overall surface free energy due to enhanced molecular heterogeneity also increases and leads to the increased density of functional groups. This results in stronger intermolecular forces with adsorbed molecules (e.g., polar solvents), thus increasing the work of adhesion. This was particularly observed with 5% 5-FU on S-DVB. 3. Mechanism of adhesion energy enhancement. The presence of 5-FU's amide and imide groups can lead to the formation of strong hydrogen bonds with polar solvents. These hydrogen bonding interactions are directional and cooperative, leading to stable adsorption layers. On the other hand, the C-F bond in 5-FU contributes to a high local dipole moment, enhancing van der Waals dipolar interactions with polarizable solvent molecules. The aromatic ring of 5-FU can engage in \(\pi\)-\(\pi\) stacking with aromatic solvents or even with the S-DVB backbone, stabilizing the surface architecture. The strong polar groups can induce dipoles in non-polar solvent molecules (Debye interactions), contributing further to adhesion. 4. Comparison with HMU and melamine. The melamine modifier has multiple amine groups but lacks the C=O/N-H polarity balance and the electronegative substituent that 5-FU has. On the other hand, 5-HMU contains hydroxyl and carbonyl groups but is less electron-withdrawing and lacks the strong dipole moment contributed by fluorine. Thus, while all modifiers increase adhesion relative to unmodified S-DVB, 5-FU offers a unique combination of strong polar interactions and molecular alignment, leading to a higher adhesion energy. The sum of the two dispersive and polar contributions of the adhesion work led to the determination of the total work of adhesion of the various solvents on the different modified copolymers. The obtained results are given in Table 4 in the form of the following equations: \(W_{a}(T)\) function of temperature, modifier, and its percentage. Two new thermodynamic parameters were defined. The first one is the surface entropy \(\Delta S_{S}\) of adhesion work and the second is relative to the surface enthalpy \(\Delta H_{S}\) of adhesion work. The general equation of \(W_{a}(T)\) can be written as follows:  
\[W_{a}(T)=\Delta H_{S}-T\Delta S_{S} \tag{19}\]  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \multicolumn{6}{c}{**S-DVBopolymer**} \\ \hline
**Solvents** & \(W_{a}(T)\) & \(\Delta S_{S}\) & \(\Delta H_{S}\) & \(T_{Mex.