# Crystallization Kinetics of an Equimolar Liquid Crystalline Mixture and Its Components
## 3 Results and Discussion
### Dielectric Relaxation Processes
We refer to this phase as SmC*, because this phase is the most probable based on the BDS results. The SmC\({}_{\rm A}\)*\(\rightarrow\) SmX\({}_{\rm A}\)* transition in the supercooled MHPOBC results in an increase and decrease in the \(\Delta\varepsilon\) of P\({}_{\rm L}\) and P\({}_{\rm H}\), respectively (Figure 7a), and an increase in the slope of the activation plot of \(\tau\) of both phasons (Figure 7b). For some compounds, an additional P\({}_{\rm hex}\) process arises at the low-frequency side of P\({}_{\rm H}\) in the SmX\({}_{\rm A}\)* phase [36; 55]. However, this was not visible for MHPOBC. Compared to MIX2 HF6 and 3F2 HPhF6, which show comparable relaxation times, the GM process is much slower and the P\({}_{\rm L}\) process is much faster for MHPOBC. The P\({}_{\rm L}\) process, probably due to overlapping with the molecular s-process, shows a linear dependence in the activation plot. The activation energy \(E_{a}\), determined by fitting the Arrhenius formula, is ca. 110 kJ/mol for all the samples. For the P\({}_{\rm H}\) process, the difference in the relaxation times between the mixture and its components is insignificant. The ionic conductivity is the highest for MIX2 HF6, slightly smaller for 3F2 HPhF6, and the lowest for MHPOBC. The MIX2 HF6 can be supercooled enough to investigate the next relaxation process on the high-frequency side of the P\({}_{\rm H}\) process (Figure 6). It can be interpreted as the molecular l-process (rotations around the long molecular axis) [56]. However, for the glass-forming materials, this process becomes the collective \(\alpha\)-process upon approaching the glass transition temperature \(T_{g}\)[57]. The \(\alpha\)-relaxation time usually shows a nonlinear dependence in the activation plot, described by the Vogel-Fulcher-Tammann formula [48; 57]:  
\[\tau_{\alpha}(T)=\tau_{\infty}\exp\biggl{(}\frac{B}{T-T_{V}}\biggr{)}, \tag{4}\]  
where \(\tau_{\infty}\) is a pre-exponential constant, \(T_{V}\) is the Vogel temperature, and \(B\) is a parameter with a unit of temperature. For the Arrhenius dependence, \(T_{V}=0\) and \(B=E_{a}/R\). The \(\alpha\)-relaxation in MIX2 HF6 cannot be investigated in the vicinity of \(T_{g}\) due to crystallization and overlap with the cr-process from the crystal phase. \(T_{g}\) is defined as the temperature at which \(\tau_{\alpha}=100\) s [57]. The \(\alpha\)-relaxation time determined at higher temperatures, down to 259 K, shows a linear dependence (Figure 9). Only two points collected upon heating after fast cooling (Figure 9h) at 257 K and 255 K deviate from the Arrhenius formula, but at the same time, they do not follow the VFT equation. Thus, the \(\alpha\)-relaxation time cannot be used for determination of the fragility index \(m_{f}\), defined as follows [57]:  
\[m_{f}=\left.\frac{d\log_{10}\tau_{\alpha}}{d\big{(}T_{g}/T\big{)}}\right|_{T=T_{ g}}, \tag{5}\]  
and describing the deviation of \(\tau_{\alpha}(T)\) from the Arrhenius formula. For strong glassformers, \(\tau_{\alpha}(T)\) follows the Arrhenius formula and \(m_{f}=16\). For very fragile glassformers, for which \(\tau_{\alpha}(T)\) dependence shows a strongly nonlinear dependence in the activation plot, \(m_{f}\) may reach more than 200. The Arrhenius behavior of \(\tau_{\alpha}\) could be interpreted as MIX2 HF6 being a strong glassformer, but the deviations from the Arrhenius formula may appear at lower temperatures (as suggested by results from 257 K and 255 K), at which \(\tau_{\alpha}\) was not investigated. Figure 8: BDS results for 3F2 HPBr6 obtained upon slow cooling: dielectric increment (**a**), activation plot of relaxation times (**b**), and activation plot for ionic conductivity (**c**). The activation energies in (**b,c**) are in kJ/mol. Figure 6: Absorption parts of selected BDS spectra of MIX2 HF6 collected on slow cooling (points), and fitting results of Equation (3) (lines) in the SmA\({}^{\star}\), SmC\({}^{\star}\) (**a**), SmC\({}_{\rm A}\)\({}^{\star}\) (**b**), and Cr (**c**) phases. The conductivity part is omitted.