## 3 Results and Discussion
### Interaction between the Cationic Modifiers and the Reactive Dyes  
#### 3.2.1 Investigation of Dye-Polymer Aqueous Solutions through UV-Vis and Fluorescence Spectroscopy  
Intermolecular interactions may affect the electronic properties of the molecular moieties with an apparent alteration of their optical absorption as well as fluorescence spectra [44; 45; 46; 47]. Both reactive dyes used in the current study contain anionic SO\({}_{3}\)\({}^{-}\) and SO\({}_{4}\)\({}^{-}\) groups, able to interact electrostatically with the cationic VBCTEAM units of the polymers. The dye with the most available interactive sites with the VBCTEAM units  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Ruby** & **Blue** & **Assignment** \\ \hline
975 m & \(\sim\)1000 m & ring bending [38] \\
1040 s & 1038 s & sym vSO\({}_{3}\)+ vCC [39; 40; 41] \\
1110 m-sh & 1118 m-sh & sym SO\({}_{2}\) str (of SO\({}_{4}\) gr) [38; 42] \\
1133 m-s & 1138 m-s & sym SO\({}_{2}\) str of C-SO\({}_{2}\)-C \\  & & vCS + vCC + v\({}_{8}\)SO\({}_{3}\)[39; 40; 41; 42; 43] \\
1183s & 1194 sh & SO\({}_{3}\) asym str [39; 41] \\
1210 sh & 1215 s & asym SO\({}_{2}\) str (of SO\({}_{4}\) gr) [38] \\
1280 sh-m & 1265 sh & C-N str [38; 42] \\
1414 w & - & C=N triazine ring str [38] \\
1615 m & 1615 m & Ring str [38] \\ \hline \hline \end{tabular}
\end{table}
Table 2: Suggested ATR-FTIR band assignment for the dyes Novacron Ruby S-3B and Remazol Brilliant Blue R.  
Figure 3: ATR-FTIR spectra of the reactive dyes Novacron Ruby S-3B and Remazol Brilliant Blue R.  
of the polymers is Novacron Ruby S-3B; five sites versus two for the case of Remazol Brilliant Blue R. However, for all dye-polymer combinations, homogeneous solutions were obtained for sufficiently low D\({}^{-}\)/P\({}^{+}\) charge ratios. Therefore, we have chosen a fixed charge ratio for all binary systems, D\({}^{-}\)/P\({}^{+}\) = 1/5, (the nominal dye negatively charged sites equal 20% of the cationic polymer sites). The absorbance and fluorescence spectra were recorded from these solutions and compared with the respective spectra of the solutions of the individual constituents.  
Figure 4a depicts the UV-Vis spectra of aqueous solutions of PVBCTEAM, Novacron Ruby S-3B dye, and the respective binary system with D\({}^{-}\)/P\({}^{+}\) = 1/5. The polymer absorption bands at 224 and 261 nm are only hardly resolved in the binary system spectra. Concerning the absorption bands of the dye, these are shifted to higher wavelengths in the binary system; depending on the transition, this redshift varies (2-15 nm), having a greater value for the n-\(\pi^{+}\) type of transition(s) observed at -500-550 nm. Alterations in the relative intensity of the bands can be resolved; however, they are not significant. Respective spectra were acquired for all dye-polymer combinations. Similar trends were noticed in all cases.  
In agreement with the absorption spectra, the fluorescence spectra (Figure 4b) of the corresponding systems exhibit spectral shifts as well. In this case, however, blueshifts are observed along with a considerable intensity increase. Hence, shifts in the range of 35-90 nm were observed in the binary system of Novacron Ruby S-3B and PVBCTEAM along with an intensity increase of the fluorescent peaks by \(\sim\)65%. Similar observations were noticed for all dye-polymer combinations.