# Shaping 1,2,4-Triazolium Fluorinated Ionic Liquid Crystals
## 3 Results and Discussion
### Thermal Analysis  
The liquid crystalline properties of neutral precursors and triazolium salts have been studied by DSC and POM analyses. A DSC analysis of each sample was performed using a heating and cooling temperature ramp of 10 \({}^{\circ}\)C min\({}^{-1}\). It was reproducible for three cycles. Neutral triazoles did not show any liquid crystalline behaviour as, upon cooling, the DSC trace showed only one exothermic peak. In general, an increase in the melting temperature (T\({}_{\text{m}}\)) of the compounds can be observed with the increase in the length of the alkyloxy chains (Table 1). The alkylation of the neutral triazoles and the formation of the corresponding salts awarded the liquid crystalline behaviour to the compounds. In all cases, at least two distinct transitions can be observed from the cooling calorimetric traces (Figure 1). The first transition of the cooling cycle after heating corresponds to the clearing point (T\({}_{\text{c}}\)) from the isotropic solution to the mesophase and the following transition as the melting point (T\({}_{\text{m}}\)). In one case, two distinct transitions can be observed before the formation of the crystals. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Neutral Triazole** & **T\({}_{\text{m}}\) (\({}^{\circ}\)C) a** & **\(\Delta\)H (kJ mol\({}^{-1}\))** \\ \hline Ph-Tri-(10)\({}_{2}\) & 22.7 & 36.8 \\ Ph-Tri-(12)\({}_{2}\) & 40.6 & 57.5 \\ Ph-Tri-(14)\({}_{2}\) & 53.2 & 76.9 \\ Ph-Tri-(16)\({}_{2}\) & 59.8 & 78.9 \\ \hline \hline \end{tabular} \({}^{\text{a}}\) Transitions refer to the second heating cycles. Temperatures indicate the onset of each peak.  
\end{table} 
Table 1: Melting temperatures (T\({}_{\text{m}}\)) and enthalpies (\(\Delta\)H) of neutral triazole compounds obtained from the DSC traces upon heating. Figure 1: DSC traces of ILCs showing the second cooling and heating cycles. Exothermic peaks point upward. The increase in the alkyloxy chain length on the phenyl ring of the triazolam salts caused an increase in T\({}_{\rm c}\), passing from 71.8 \({}^{\circ}\)C to 102.7 \({}^{\circ}\)C for [**Ph-Tri-(10)\({}_{2}\)][OTf**] and [**Ph-Tri-(16)\({}_{2}\)][OTf**], respectively (Table 2). However, [**Ph-Tri-(14)\({}_{2}\)][OTf**] showed a deviation from the above trend as a decrease in T\({}_{\rm c}\) value was recorded for this salt. The observed increase in clearing points with an increasing chain length are in agreement with what was previously reported as longer hydrocarbon chains increase the van der Waals forces among the alkoxy moieties, inducing micro-segregation between the hydrophobic alkyl chains and charged ionic regions [10]. Interestingly, passing from 14 hydrocarbon chains to longer alkyloxy chains (16), more than one transition can be recognized and, moreover, the transitions to mesophases are observable both in cooling and heating ramps. Comparing the data from Table 2 with the literature, the transition temperatures and the corresponding enthalpies could be suggestive of phase transitions [2; 31]. From the enthalpy values, it can be assumed that, in all cases, the first exothermic peak can be ascribed to a transition from the isotropic liquid into the liquid crystalline phase (Iso-LC). The second transition probably refers to the transition from the liquid crystalline phase into the crystalline solid-state form (LC-Cr) when only two exothermic peaks appear in DSC, i.e., [**Ph-Tri-(10)\({}_{2}\)][OTf**], [**Ph-Tri-(12)\({}_{2}\)][OTf**] and [**Ph-Tri-(14)\({}_{2}\)][OTf**]. On the other hand, for [**Ph-Tri-(16)\({}_{2}\)][OTf**], a different scenario is observed: three exothermic peaks appear in the DSC trace. A transition between two different liquid crystalline phases can be hypothesized before the formation of a crystalline phase, even if the enthalpy value associated to a possible LC-LC transition seems high. The combination of DSC data and the POM analysis can shed light on the transitions occurring during the heating and cooling cycles of the salts.