## 2 Results and Discussion
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**No.** & **Temperature [\({}^{\circ}\)C]** & **Catalyst** & **Time [h]** \\ \hline T1 & 20 & - & 24 \\ T2 & 25 & - & 23 \\ T3 & 30 & - & 23 \\ T4 & 50 & - & 22 \\ T5 & 70 & - & 25 \\ T6 & 90 & - & 23 \\ T7 & 110 & - & 25 \\ C1 & 30 & DBU & 4 \\ C2 & 30 & Ph3P & 3 \\ C3 & 50 & DBU & 3 \\ C4 & 50 & Ph3P & 3 \\ C5 & 50 & Sn(II) & 3 \\ C6 & 50 & Sn(IV) & 3.5 \\ C7 & 50 & DABCO & 3 \\ C8 & 50 & Ti(IV) & 3 \\ C9 [FOOTNOTE:]Footnote : Product was subjected to vacuum distillation in order to remove ethanol from the system. \({}^{\circ}\) Reaction was carried out for 6.5 h, including 3 h at atmospheric pressure and 3.5 h under diminished pressure (vacuum distillation).[ENDFOOTNOTE] & 50 & Ti(IV) & 3 + 3.5 \({}^{\mathrm{b}}\) \\ C10 & 50 & Zn(II) & 4 \\ C11 & 50 & Zr(IV) & 4.5 \\ C12 & 50 & TEA & 4.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Conditions and catalysts used in the reactions of EC with APTES. application of vacuum in order to remove polycondensation by-product (ethanol, l and m), resulted in some changes in products structure. For instance, there was a separation of signals from methylene (b, 3.8 ppm) protons in oxyethylene groups and the signals from methylene groups next to oxygen atoms of the hydroxyl group (g', 3.9 ppm). In addition, the signals of protons bond to oxygen and nitrogen atoms in carbamate (i, 5.18 ppm) groups became more extensive. For a quantitative analysis of reaction progress and products, the conversion of EC together with ethanol evolution was measured by means of GC, which allowed us to determine the formation of, respectively, the main monomeric product (APTES-OH) and oligomeric side products. It gives some correlation between the reaction rate and selectivity. The results plotted over time are shown in Figures 4 and 5. It was found that with no catalyst under rising temperature, the rate of EC conversion increased significantly; however, it also produced a large amount of by-products resulting from the condensation of the hydroxyl monomer (Figure 4). When analyzing the EC conversion, it was noticed that at 20 \({}^{\circ}\)C after 20 min, the EC conversion was 47.9%, and the content of ethanol was 0%, while after 24 h, it was 95.3% and just 1.13%, respectively. On the other hand, at 110 \({}^{\circ}\)C, these values were 89.6% and 51.1% after 20 min, and also 98.7% and 72.3% after 24 h, accordingly. Comparing all the results, it can be concluded that the APTES-OH synthesis process runs rather slowly but selectively at low temperatures up to 30 \({}^{\circ}\)C. On the other hand, if vigorous oligomerization of APTES-OH is necessary, a temperature above 50 \({}^{\circ}\)C should be applied, so the conversion of the reactants is much faster, and the condensation reaction becomes significant. The siloxane exchange of the ethoxy groups with the hydroxyl groups of the  
Figure 3: \({}^{1}\)H NMR spectrum of products in CDCl\({}_{3}\). monomer APTES-OH or its hydroxyl oligomeric derivatives, which leads to the production of ethanol and condensation products, occurs satisfactorily at higher temperatures. When organic catalysts were introduced to these processes carried out at 30 \({}^{\circ}\)C, it slightly increased the EC conversion rate (especially for DBU), whereas at 50 \({}^{\circ}\)C, in the case of metal-based and organic catalysts, the differences were negligible and, moreover, for Ti(IV), Zn(II) and Ph\({}_{3}\)P systems, the conversion rate was even lower. However, in all these processes, the presence of a catalyst accelerated moderately or significantly the reaction of APTES-OH condensation. It is worth noting that at 50 \({}^{\circ}\)C, when using catalysts based on Sn(II), Zn(II), or Ti(IV), the APTES-OH content did not exceed 20% (for Ti(IV), it did not exceed 5%) in any studied EC conversion, although the latter one finally reached above 85%.