## 3 Results and Discussion
### Study of the Interactions  
In order to obtain information about the behaviour of each protective when applied on the stone surface and on possible interactions between the two materials, \({}^{19}\)F MAS NMR spectra of the Fluoline HY and Fluo AQ were recorded, together with the T\({}_{1}\)F and T\({}_{2}\)F relaxation times before and after their application on the stone. \({}^{19}\)F MAS NMR spectra of Fluoline HY and Fluo AQ after their application on the stone sample are shown in Figures 13 and 14. In the spectra of the Fluoline HY and of Fluo AQ on the stone, chemical shift values very similar to those of the pure polymers were observed. Nevertheless, by comparing \begin{table}
\begin{tabular}{c c c} \hline
**Peak** & **Chemicals Shift (Ppm)** & **Assignment** \\ \hline
1 & 176.89 & RO\(-\)(C=O)\(-\) \\
2 & 56.84 & \(-\)O\(-\)CH\({}_{3}\) \\
3 & 45.37 & \(-\)CH\({}_{2}\)\(-\)CF\({}_{2}\)\(-\) \\
4 & (0–40) & \(-\)CH\({}_{2}\)\(-\)CH\({}_{2}\)\(-\) \\ \hline \end{tabular}
\end{table} 
Table 6: Assignment of the chemical shift of \({}^{13}\)C[\({}^{1}\)H] CP-MAS spectrum. Figure 14: \({}^{19}\)F MAS NMR spectra of **(a)** Fluo AQ on stone; **(b)** Fluo AQ on stone (black) and Fluo AQ film (red). The symbol (\(\downarrow\)) represents the spinning side bands. Figure 12: Sequence of repetitive units in Fluo AQ. Figure 13: \({}^{19}\)F MAS NMR spectrum of **(a)** Fluoline HY on stone and **(b)** overlapping with the Fluoline HY film spectrum (red line). The symbol (\(\downarrow\)) represents the spinning side bands. these spectra with those of pure polymers, an intensity increase in the spinning side bands (\(\downarrow\)) is observed (see Figures 13a and 14a). This provided evidence that the polymer assumes preferential orientations inside the stone pores, thus resulting in a more organized and less mobile material. This hypothesis was confirmed by the analysis of the spin-lattice relaxation times (T\({}_{1}\)F) and spin-spin relaxation times (T\({}_{2}\)F) shown in Tables 7 and 8. T\({}_{1}\)F values for the two polymers in contact with the stone are longer than the relaxation times of the pure materials. This T\({}_{1}\)F increase suggests that the local molecular motions in the order of MHz decrease after the application [34]. T\({}_{2}\)F values of Fluoline HY in contact with the stone are shorter than those of pure Fluoline HY in accordance with the fact that signals 1 and 2 of Fluoline HY in contact with the stone are broader than the homologous bands of pure polymer (see Figure 13b). This indicates that even the low-frequency motions involving the side chains are prevented within the pores of the stone. T\({}_{2}\)F of the FluO AQ does not change after the application on the stone. This provides evidence that the low-frequency motions of the side chains are not affected by the confinement effect of the polymer. This could indicate that the partially cross-linked structure of this polymer could prevent changes in the dynamic state of the side chains after its application on the stone material. All these findings can be correlated with the observed macroscopic properties. The crosslinking of the polymeric system could cause the formation of a more homogeneous surface film. This could be related to the greater water repellence imparted onto the stone substrate compared to Fluoline HY and to the unchanged breathability of the stone after treatment, in agreement with the results obtained from the investigation by X-ray microscopy. The molecular structure and dynamics of the polymer chains are responsible for a different structural organization of the polymers in contact with the stone substrate. The different structural organization of the polymers provides indirect evidence of the different efficacy of hydrophobic treatments and justifies their observed different spatial distribution, confirming the correlation with the observed macroscopic properties.