# Multifunctional Modifying Systems Based on Ionic Liquids for Epoxy Resin Systems and Composites
## 3 Results and Discussion  
### Synthesis and Preparation of Modification Formulations Based on Ionic Liquids  
In the first stage of the research, modification systems based on six ionic liquids were produced. The goal was to produce such systems that would differ in (i) the chemical structure of the components, (ii) the content of phosphorus and silicon and the ratio of the two to each other, and (iii) the form of phosphorus bonding in the ionic liquid molecule (tertiary phosphorus atom in the cation or phosphorus in the form of organic phosphate). This goal was achieved, and the mixtures produced remained stable throughout the research period. Nevertheless, it should be noted that all the ionic liquids selected in the study were present at room temperature in the liquid state, which greatly facilitated their preparation. On the basis of the conducted studies, it was observed that the greater the similarity of the cation structure of the two components of the mixture, the more homogeneous it was \begin{table}
\begin{tabular}{c c c c c} \hline \hline \begin{tabular}{c} **Modification** \\ **System** \\ \end{tabular} & \begin{tabular}{c} **IL 1–P Donor** \\ **(1 eq.)** \\ \end{tabular} & \begin{tabular}{c} **IL 2–Si Donor** \\ **(1 eq.)** \\ \end{tabular} & \begin{tabular}{c} **Total Molecular** \\ **Weight** \\ **[g/mol]** \\ \end{tabular} & \
\begin{tabular}{c} **\% P** \\ \end{tabular} &
\begin{tabular}{c} **\% Si** \\ \end{tabular} \\ \hline A & [EMIM] [dmp] & [TMSPrMIM] [Cl] & 587 & 5.3 & 4.8 \\ \hline B & [EMIM] [dep] & [TMSPrMIM] [Cl] & 559 & 5.5 & 5.0 \\ \hline C & [EMIM] [dbp] & [TMSPrMIM] [Cl] & 643 & 4.8 & 4.4 \\ \hline D & [P6614] [btmp] & [TMSPrMIM] [Cl] & 1128 & 5.5 & 2.5 \\ \hline E & [P6614] [behp] & [TMSPrMIM] [Cl] & 1096 & 5.7 & 2.6 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Parameters of modification systems based on ILs. (mixtures A, B, and C). In contrast, when the ionic liquids differ significantly in their structure (D and E), the formation of emulsions, rather than homogeneous systems, was observed. The emulsion phenomenon is more pronounced, the longer a given mixture is stored and manifests itself in the gradual disintegration of the emulsion into individual phases. Despite the use of elevated temperatures during the preparation of mixtures, this effect could not be eliminated. The observed phenomenon seems to be typical for these types of systems and well understood, if only during studies considering formation of eutectic mixtures of ionic liquids. Two or more ionic liquids will therefore form more stable and homogeneous systems with each other if their structural similarity is greater and they can commonality the individual ions in their composition. The process of formation of the final epoxy system is shown graphically in Figure 3. The total content of ionic liquids in the system varies at about 12% by weight, with about 2% by weight being [EMIM] [dca], which acts as a cure initiator (CA) in the epoxy system. The mode of action and properties of this liquid as a curing agent have been studied by numerous groups of scientists [32; 45; 46; 47; 48], and it is because this substance is so well known that it was chosen for this study. The polymerization of the epoxy resin initiated by [EMIM] [dca] starts around 80-100 \({}^{\circ}\)C, depending on the type of resin. The process is characterized by the presence of two thermal peaks on the DSC thermogram, which can indicate simultaneous cationic polymerization (initiated by IL cation) and anionic polymerization (initiated by [dca] anion). The polymerization peak occurs in the temperature range of 140-180 \({}^{\circ}\)C. After the epoxy resin system is properly prepared with CA, a previously prepared modifying system based on phosphorus- and silicon-donor ILs is added with an amount of 10% by weight. Therefore, five homogeneous epoxy systems were obtained that remained stable for the duration of the conducted tests and did not cure at room temperature for at least 30 days (the test period).