## 4 Conclusions  
A new method was proposed to determine the variations in the work of adhesion \(W_{a}(T)\) of model organic solvents on S-DVB copolymers modified by melamine, 5-HMU, and 5-FU at different percentages by varying the temperature. The surface properties of modified copolymers such as the dispersive and polar free energy of adsorption and the London dispersive and polar surface energies of copolymers were used to determine the dispersive \(W_{a}^{\rm d}(T)\) and polar \(W_{a}^{\rm p}(T)\) works of adhesion of the various organic model solvents on S-DVB copolymers as a function of temperature and modifier percentage. Results showed an excellent linearity of \(W_{a}^{\rm d}(T)\) and \(W_{a}^{\rm p}(T)\) as a function of temperature for all solvents and copolymers, with a decrease in the temperature depending on the modifier's nature and its percentage. The highest polar adhesion work was obtained with ethanol on S-DVB modified by melamine, while the values of \(W_{a}^{\rm p}(T)\) of benzene and toluene were the lowest. The comparison between the various modifiers led to the conclusion that the maximum adhesion work was obtained with 5-FU on the S-DVB copolymer. Indeed, the modification of S-DVB by 5-FU with high-energy interaction sites increases compatibility \begin{table}
\begin{tabular}{c c c c} \hline
**Copolymer** & **Equations \(\Delta H_{S}\)=f(\(\Delta S_{S}\))** & \(T_{S}\) & \(\bf R^{2}\) \\ \hline S-DVB Copolymer & \(\Delta H_{S}=527.12\ \Delta S_{S}-23.502\) & 527.12 & 0.9923 \\ \hline
1\% Melamine/S-DVB Copolymer & \(\Delta H_{S}=476.71\ \Delta S_{S}+42.251\) & 476.71 & 0.9672 \\ \hline
2\% Melamine/S-DVB Copolymer & \(\Delta H_{S}=543.47\ \Delta S_{S}-1.841\) & 543.47 & 0.9596 \\ \hline
3\% Melamine/S-DVB Copolymer & \(\Delta H_{S}=500.3\ \Delta S_{S}+18.342\) & 500.3 & 0.9957 \\ \hline
4\% Melamine/S-DVB Copolymer & \(\Delta H_{S}=532.74\ \Delta S_{S}+1.972\) & 532.74 & 0.9882 \\ \hline
1\% 5-HMU/S-DVB Copolymer & \(\Delta H_{S}=494.38\ \Delta S_{S}+9.860\) & 494.38 & 0.9917 \\ \hline
3.5\% 5-HMU/S-DVB Copolymer & \(\Delta H_{S}=546.19\ \Delta S_{S}-25.452\) & 546.19 & 0.9838 \\ \hline
10\% 5-HMU/S-DVB Copolymer & \(\Delta H_{S}=609.06\ \Delta S_{S}-86.224\) & 609.06 & 0.9884 \\ \hline
1\% 5-Fluoracil/S-DVB Copolymer & \(\Delta H_{S}=558.33\ \Delta S_{S}-11.407\) & 558.33 & 0.9793 \\ \hline
5\% 5-Fluoracil/S-DVB Copolymer & \(\Delta H_{S}=534.46\ \Delta S_{S}-0.318\) & 534.46 & 0.9803 \\ \hline
10\% 5-Fluoracil/S-DVB Copolymer & \(\Delta H_{S}=556.11\ \Delta S_{S}-14.185\) & 556.11 & 0.973 \\ \hline \end{tabular}
\end{table} 
Table 6: Equations of \(\Delta H_{S}\) as a function of \(\Delta S_{S}\) of the different modified copolymers with the values of \(T_{S}\) and the corresponding linear regression coefficients. and adhesion with a wide range of solvents. This shows that the careful selection of modifiers with tailored molecular functionalities can effectively regulate the polar surface energy and adhesion behavior. The work of adhesion was correlated to the surface enthalpy \(\Delta H_{S}\) and entropy \(\Delta S_{S}\) of organic solvents adsorbed on copolymers at different modifier percentages (\(q\)) via the following equation:  
\[W_{a}(T,q)=\Delta H_{S}(q)-T\Delta S_{S}(q) \tag{24}\]  
It was proved that \(\Delta H_{S}(q)\) and \(\Delta S_{S}(q)\) linearly varied as a function of the modifier percentage (\(q\)). The results in Table 5 led to the following general equations:  
\[\Delta H_{S}(q)=aq+b \tag{25}\]  
\[\Delta S_{S}(q)=cq+d \tag{26}\]  
A new relation of the work of adhesion \(W_{a}(T,q)\) function of the two variables \(T\) and \(q\) was therefore proposed:  
\[W_{a}(T,q)=aq+b-T(cq+d) \tag{27}\]  
Furthermore, linear relations of the surface enthalpy of adhesion work \(\Delta H_{S}\) as a function of the surface entropy of adhesion were obtained and a new surface temperature \(T_{S}\) representing an isokinetic surface temperature was defined.