## 2 Materials and Methods
### Synthesis of Sol-Gel Silica Materials  
The silica materials were prepared using the sol-gel method in a similar way to that previously reported [27]. In this work, tetraethoxysilane (TEOS) was used as a silica source, and silane precursors (ethoxydimethylvinylsilane (DMVES), triethoxyoctylsilane (OTES), and trimethoxyhexadecylsilane (HDTMES)) were used as modifying agents (see Table 1).  
In the first step, TEOS and silane precursors (DMVES, OTES, or HDTMES) were pre-hydrolyzed with iPrOH (15 mL) and HCl (0.1 M, 0.46 mL) for 4 h, under continuous stirring at room temperature (25 \(\pm\) 2 \({}^{\circ}\)C). The solutions were prepared by mixing TEOS/silane precursors in a molar ratio of 1:1. As a second step, MA (0.1 g) was added to the solutions in order to start the condensation reactions. After complete dissolution of MA, a well-defined amount of TIP (0.4 mL) was slowly added. The crosslinking agent (TIP) was added in the second part of the recipe to avoid the formation of precipitation. Further amounts of HCl (0.1 M, 2 mL) and FIN (0.2 mL) were introduced to the solutions in order to continue the sol-gel process and initiate the photopolymerization reaction. The mixtures were stirred for another 2 h, at room temperature (25 \(\pm\) 2 \({}^{\circ}\)C), obtaining two stable, transparent, and homogeneous solutions: TEOS/DMVES/OTES (A) and TEOS/DMVES/HDTMES (B) (see Table 2).  
Two different powders were obtained when these mixtures were placed into plastic vials. Furthermore, two films were realized when these mixtures were deposited onto the PVC substrates through draw-down sample coating with the manual applicator. All samples were irradiated under a UV lamp (\(\lambda\) = 365 nm, 10 min, irradiance of 2290 mW/cm\({}^{2}\)) in order to initiate the photopolymerization reaction. After that, all final materials were dried, kept (overnight) at room temperature (25 \(\pm\) 2 \({}^{\circ}\)C), and then characterized.  
The obtained powders were analyzed by Fourier-transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA). The properties of final thin films were determined through UV/Vis spectroscopy, atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and water contact-angle measurements.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Alkoxysilane** & **Structure** & **Molecular Formula** & **M\({}_{\text{w}}\) (g-mol\({}^{-1}\))** \\ \hline TEOS & \(H_{3}\)C & \(C_{8}\)H\({}_{20}\)O\({}_{4}\)Si & 208.33 \\ DMVES & \(H_{2}\)C & \(C_{6}\)H\({}_{14}\)OSi & 130.26 \\ OTES & \(H_{3}\)C & \(C_{14}\)H\({}_{32}\)O\({}_{3}\)Si & 276.48 \\ HDTMES & \(CH_{3}\)(CH\({}_{2}\))\({}_{15}\)–Si\(\cdot\)OCH\({}_{3}\) & \(C_{19}\)H\({}_{42}\)O\({}_{3}\)Si & 346.63 \\ \end{tabular}
\end{table}
Table 1: Detailed information of alkoxysilanes used in this experiment.  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline
**Sample** & **TEOS (mL)** & **DMVES (mL)** & **OTES (mL)** & **HDTMES (mL)** \\ \hline A & 4.2 & 1.52 & 2.9 & - \\ B & 4.2 & 1.52 & - & 0.7 \\ \hline \hline \end{tabular}
\end{table}
Table 2: Alkoxysilanes used for the preparation of the sol-gel silica materials.