## 2 Results and Discussion
The main population (Supplementary Materials Figure S1, structure S1.1) turned out to be the linear and/or branched oligomer formed during condensation, with the repeating unit of 263.12 g/mol flying with K+ ions, m/z of end group 46.51 g/mol (the distribution indicated with n\({}_{\mathrm{x}}\) in Figure 7). The other existing but much less intensive population is characterized by the same \(m/z\) value of the repeating units but with a different mass of end groups of 142.29 g/mol. The intensity of this population increases when the process conditions become more severe. However, the authors of this paper were unable to assign any structure to it. The possible structures formed in the following reactions considered were: attachment of two EC molecules to one APTES molecule, formation of a partial network of Si-O-Si bonds, intramolecular cyclization with the release of EC or ethylene glycol, etc., presented in Figure S1 (structure S1.3-S1.9). The repeat units and the masses of the end groups of the proposed structures are listed in Table S1. Additionally, for all products examined (T2, C8 and C9), one can find a population of very low intensity resulting from macrocycles generated in the process of intramolecular condensation, with the repeating unit of 263.12 g/mol fluing with K\({}^{+}\) ions, \(m/z\) of end group 0.37 g/mol (the distribution is marked with c\({}^{\mathrm{x}}\) in Figure 7). The structure is shown in Figure S1 (structure S1.2). Surprisingly, for sample T2, the signals for the monomer, dimer, trimer and tetramer are present on MALDI-ToF analysis, but the one for the dimer is the most intensive, whereas APTES-OH monomer was the major product indicated by GPC analysis of the concerned sample. Although the MALDI ToF analysis is not quantitative, it should be expected that APTES-OH monomer molecules with the lowest molar mass, and thus most willingly flying  
Figure 6: GPC molar mass distribution for T2 (25 \({}^{\circ}\)C, without catalyst), C8 (50 \({}^{\circ}\)C, Ti(IV)) and C9 (50 \({}^{\circ}\)C, Ti(IV), vacuum) products (n\({}^{\mathrm{t}}\)x—theoretical value of the molar mass for a particular number of x units). under the measurement conditions, which we would expect the most in the T2 sample, should be visible on the spectrum in the signal with the highest intensity. It was suspected that before or during the MALDI ToF experiment, the sample partially underwent some undesirable processes (e.g., monomer distillation or condensation driven by a high vacuum in the instrument chamber). In order to verify this hypothesis, the esterification reaction of the T2 product with oleic acid in the presence of dicyclohexyl carbodiimide was carried out, resulting in the derivative T\({}_{\text{OAE}}\), which was not able to self-condense and was much less volatile. Figure 7: MALDI-ToF analysis for T2 (RT, without catalyst), C8 (50 \({}^{\circ}\)C, Ti(IV)) and C9 (50 \({}^{\circ}\)C, Ti(IV), vacuum) products. When analyzing the obtained MALDI-ToF result for the T2 OAE sample (Figure 8), the absence of T2 and its oligomers can be confirmed (no signals from unesterified monomer, dimer, trimer, etc. ), while signals of the corresponding oleic acid esters were present (n\({}_{\mathrm{x}}\) distribution, \(m/z\) of repeating unit of 263.12 g/mol, \(m/z\) of end group 310.27 g/mol). In addition, there is a minor distribution from the population of a similar structure, in which the release of one EC molecule contained in the end group occurred during the reaction of the APTES-OH monomer and oligomers with oleic acid (n\({}_{\mathrm{x}}\) distribution, \(m/z\) of repeating unit of 263.12 g/mol, \(m/z\) of end group 222.30 g/mol, which is 88 g/mol less than for n\({}_{\mathrm{x}}\) population), forming an amide bond instead of an ester one.