## 3 Results
### Polar (Lewis Acid-Base) Surface Energy of Modified Copolymers  
First, the polar acid \(\gamma_{s}^{+}\) and base \(\gamma_{s}^{-}\) surface energies of modified copolymers were obtained using the method of [PERSON] et al. (2018). This led to the values of the polar surface energy \(\gamma_{s}^{p}\) and consequently to those of the total surface energy \(\gamma_{s}^{tot. }\) obtained as a function of temperature using the previous equations and the results of \(\gamma_{s}^{d}(T)\). The values of \(\gamma_{s}^{p}(T)\) of the copolymers are given in Table 2. They show that the modifier 2% melamine on the S-DVB copolymer exhibited the highest polar surface energy, followed by 5% 5-Fu/S-DVB. The lowest \(\gamma_{s}^{p}(T)\) was observed with 1% 5-Fu/S-DVB. The results in Table 2 clearly show the significant effect of the temperature and modifier on the polar surface energy. To highlight the effect of the modifier percentage on the \(\gamma_{s}^{p}\) of the different modified copolymers, the curves of \(\gamma_{s}^{p}\) of solid surfaces are plotted in Figure 2 as a function of the modifier percentage. The variations in \(\gamma_{s}^{p}\) for all used modifiers are not linear when the modifier percentage varies. The results show a maximum of \(\gamma_{s}^{p}\) at 2% melamine/S-DVB and a minimum at 3% of melamine for all temperatures with a paliler after 4% melamine (Figure 2a). However, a minimum of \(\gamma_{s}^{p}\) was observed at 1% of 5-HMU (Figure 2b) and 5-FU (Figure 2c) for the different temperatures, and a pallier shown in Figure 2 after 4% of the modifier on the S-DVB copolymer. The results thus prove that the polar surface energy is strongly affected not only by the temperature but also by both the nature and the percentage of the modifier, as is shown in Figure 3. It seems that the S-DVB copolymer modified by melamine gives the highest \(\gamma_{s}^{p}\) at 2% melamine, while the 5-FU on S-DVB exhibits the highest \(\gamma_{s}^{p}\) after 4% 5-FU. \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**Temperature T (K)** & **453.15** & **458.15** & **463.15** & **468.15** & **473.15** & **Equation \(\gamma_{s}^{p}(T)\)** & \(\mathbf{R}^{2}\) \\ \hline S-DVB copolymer & 81.54 & 76.29 & 71.17 & 66.19 & 61.33 & \(\gamma_{s}^{p}(T)=-1.01\) T + 539.27 & 0.9998 \\ \hline
1\% Melamine/S-DVB & 70.11 & 68.03 & 65.99 & 64 & 62.07 & \(\gamma_{s}^{p}(T)=-0.40\) T + 252.32 & 0.9998 \\ \hline
2\% Melamine/S-DVB & 124.35 & 120.53 & 116.81 & 113.18 & 109.63 & \(\gamma_{s}^{p}(T)=-0.74\) T + 457.69 & 0.9998 \\ \hline
3\% Melamine/S-DVB & 54.36 & 50.34 & 46.51 & 42.87 & 39.41 & \(\gamma_{s}^{p}(T)=-0.75\) T + 392.86 & 0.9991 \\ \hline
4\% Melamine/S-DVB & 84.71 & 79.24 & 73.99 & 68.97 & 64.16 & \(\gamma_{s}^{p}(T)=-1.03\) T + 550.05 & 0.9994 \\ \hline Temperature T(K) & 453.15 & 458.15 & 463.15 & 468.15 & 473.15 & Equation \(\gamma_{s}^{p}(T)\) & \(\mathrm{R}^{2}\) \\ \hline
1\% 5-HMU/S-DVB & 36.89 & 35.08 & 33.04 & 31.34 & 29.61 & \(\gamma_{s}^{p}(T)=-0.37\) T + 202.7 & 0.9990 \\ \hline
3.5\% 5-HMU/S-DVB & 73.56 & 69.12 & 63.85 & 59.40 & 54.90 & \(\gamma_{s}^{p}(T)=-0.94\) T + 499.9 & 0.9992 \\ \hline
10\% 5-HMU/S-DVB & 78.82 & 74.47 & 69.42 & 65.06 & 60.66 & \(\gamma_{s}^{p}(T)=-0.92\) T + 493.28 & 0.9994 \\ \hline Temperature T(K) & 453.15 & 458.15 & 463.15 & 468.15 & 473.15 & Equation \(\gamma_{s}^{p}(T)\) & \(\mathrm{R}^{2}\) \\ \hline
1\% 5-FU/S-DVB & 23.61 & 21.01 & 18.60 & 16.35 & 14.28 & \(\gamma_{s}^{p}(T)=-0.47\) T + 234.78 & 0.9980 \\ \hline
5\% 5-FU/S-DVB & 105.08 & 96.96 & 89.26 & 81.96 & 75.06 & \(\gamma_{s}^{p}(T)=-1.50\) T + 784.76 & 0.9990 \\ \hline
10\% 5-FU/S-DVB & 98.84 & 93.37 & 88.12 & 83.08 & 78.23 & \(\gamma_{s}^{p}(T)=-1.03\) T + 565.47 & 0.9994 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Variations in polar surface energy \(\gamma_{s}^{p}(T)\) (in mJ/m\({}^{2}\)) of modified copolymers and the corresponding linear equations.