## 3 Results and Discussion
### Physicochemical Properties of HMS-SO\({}_{3}\)H and NRHMS-SO\({}_{3}\)H
HMS-SO\({}_{3}\)H possessed higher acidity than NRHMS-SO\({}_{3}\)H at the same MPTMS loading level due to higher sulfur content. Furthermore, XPS analysis was used to quantitate the sulfonic acid groups, thus acidity, at the external surface of synthesized materials. In all cases, the acidity obtained via both techniques was lower than the theoretical acidity, calculated from the total sulfur content. This result confirmed that some thiol groups were not fully oxidized to sulfonic acid groups. The external surface acidity was comparable with the total acidity for both materials synthesized with the MPTMS/TECS ratios of 0.2 and 0.4. It indicates a uniform distribution of sulfonic acid groups inside the primary mesopores and on the material external surface [24]. However, at an increased MPTMS loading level, the acidity obtained via the acid-base titration (0.90 mmol/g and 0.80 mmol/g for HMS-SO\({}_{3}\)H (0.6) and NRHMS-SO\({}_{3}\)H (0.6), respectively) was noticeably less than that determined by the XPS analysis (1.16 mmol/g and 1.29 mmol/g for HMS-SO\({}_{3}\)H (0.6) and NRHMS-SO\({}_{3}\)H (0.6), respectively). It was explained by the presence of some inaccessible sulfonic acid groups due to the non-uniform distribution of the functional groups at the pore entrance and on the external surface. The formation of the mesostructured NRHMS-SO\({}_{3}\)H material series is depicted in Scheme 1. Firstly, TEOS was infiltrated in NR via the hydrophobic interaction between the polymeric chain of NR and remnant ethoxy groups from silica precursors [44]. During the formation of the nanocomposite mesophase via cooperative self-assembly [28], the functional group precursors were uniformly distributed on the external surface within the mesoporous network and embedded in the sublayer of the silica framework. Additionally, NR induced the hydrophobic interaction between NR and silica precursors (TEOS and \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline
**Sample** & \begin{tabular}{c} **S\({}_{\text{SET}}\)****a** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **S\({}_{\text{SET}}\)****b** \\ **(m\({}^{2}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{T}}\)****c** \\ **(m\({}^{3}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{P}}\)****a** \\ **(m\({}^{3}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **D\({}_{\text{P}}\)****e** \\ **(m\({}^{3}\) g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **d\({}_{\text{100}}\)****f** \\ **(m\({}^{3}\)** **g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **a\({}_{\text{0}}\)****g** \\ **(m\({}^{3}\)** **g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **W\({}_{\text{T}}\)****h** \\ **(m\({}^{3}\)** **g\({}^{-1}\))** \\ \end{tabular} & \begin{tabular}{c} **V\({}_{\text{m, H2O}}\)****i** \\ **(m\({}^{3}\)** **g\({}^{-1}\))** \\ \end{tabular} \\ \hline \begin{tabular}{c} HMS-SO\({}_{3}\)H \\ (0.2) \\ \end{tabular} & 901 & 211 & 0.97 & 0.35 & 2.20 & 3.84 & 4.43 & 2.23 & 63.8 \\ \begin{tabular}{c} HMS-SO\({}_{3}\)H \\ (0.4) \\ \end{tabular} & 580 & 117 & 0.80 & 0.16 & 2.05 & 4.01 & 4.63 & 2.58 & 68.2 \\ \begin{tabular}{c} HMS-SO\({}_{3}\)H \\ (0.6) \\ \end{tabular} & 279 & 37 & 0.41 & 0.12 & 2.05 & _n.d._ & _n.d._ & _n.d._ & 72.8 \\ \begin{tabular}{c} NRHMS-SO\({}_{3}\)H \\ (0.2) \\ \end{tabular} & 594 & 177 & 0.81 & 0.17 & 2.15 & 4.01 & 4.63 & 2.48 & 56.7 \\ \
\begin{tabular}{c} NRHMS-SO\({}_{3}\)H \\ (0.4) \\ \end{tabular} & 400 & 125 & 0.71 & 0.13 & 2.05 & 4.30 & 4.97 & 2.92 & 58.1 \\
\begin{tabular}{c} NRHMS-SO\({}_{3}\)H \\ (0.6) \\ \end{tabular} & 194 & 47 & 0.36 & 0.07 & 2.05 & _n.d._ & _n.d._ & _n.d._ & 65.8 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Physicochemical properties of HMS-SO\({}_{3}\)H and NRHMS-SO\({}_{3}\)H series. MPTMS), resulting in the NR incorporation in the mesoporous silica framework [45].