## 2 Results
### Thermal Properties and Phase Behavior  
The thermal properties and phase transitions of the pure additive molecules and the electrolytes were measured using differential scanning calorimetry (DSC) and small and wide-angle X-ray scattering (SAXS/WAXS). Figure 2 shows the DSC scans for the measured ratios of C18 RS:C18 LiTFSI along with the pure C18 RS compounds during the heating and cooling cycles. Upon cooling, a morphological phase transition (later confirmed via scattering to be a smectic to isotropic transition) and crystallization are apparent. Upon heating, the blended electrolytes undergo obvious cold crystallization and melting transitions. Importantly, the blended electrolytes undergo a limited number of thermal transitions observable using DSC, and no transitions unique to the pure additives, indicating that macrophase separation of the two components may be avoided. Temperature values measured for the melting points and smectic to isotropic transition are shown in Table 1.  
Figure 1: Molecular structures of C18 LiTFSI and additive sulfonyl molecules. Figure 2: DSC scans for mixed ratios of additive molecules and C18 LiTFSI in addition to pure additive on first cooling and second heating cycles. (**a**) C18 MS cooling, (**b**) C18 MS heating, (**c**) C18 ES cooling, (**d**) C18 ES heating, (**e**) C18 IPS cooling, and (**f**) C18 IPS heating show exothermic transitions pointed up. On the cooling cycles, isotropic to smectic transitions are indicated by *. Data for C18 LiTFSI were originally reported in [21]. Compared to C18 LiTFSI, the addition of the additive molecules has little to no effect on melting point (crystalline to smectic). However, as the C18 LiTFSI becomes more dilute due to the addition of the additive molecules, the smectic phase occurs over a smaller temperature range. None of the three additive molecules have liquid crystal phases when pure. This trend based on the ratio of additive holds for all three molecules; however, phase transition temperatures also become lower overall with larger sulfonyl-alkyl groups. The melting points and the smectic to isotropic transitions occur at lower temperatures, with the trend more pronounced at higher ratios (Figure 3). Interestingly, C18 ES blends most resemble C18 MS blends at low concentrations and C18 IPS blends at higher ratios before total loss of the smectic phase. SAXS and WAXS measurements that show the phases of the material at various temperatures corroborate phase data observed through DSC and confirm the existence of a lamellar smectic phase for the materials over certain temperatures, as illustrated in Figure 4. \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline \multirow{2}{*}{**Material**} & \multirow{2}{*}{\(\mathbf{T_{c}}\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\begin{tabular}{c} **Isotropic to** \\ **Smectic** \\ **Transition** (\({}^{\circ}\)C) \\ \end{tabular} } & \multirow{2}{*}{\(\mathbf{T_{c}}\) (\({}^{\circ}\)C)} & \multirow{2}{*}{\begin{tabular}{c} **Isotropic to** \\ **Smectic** \\ **Transition** (\({}^{\circ}\)C) \\ \end{tabular} } & & & & \
\begin{tabular}{c} **Isotropic to** \\ **Smectic** \\ **Transition** (\({}^{\circ}\)C) \\ \end{tabular} & & & &
\begin{tabular}{c} **Smectic** \\ **Transition** (\({}^{\circ}\)C) \\ \end{tabular} \\ \hline C18 LiTFSI & 63 & 199 & C18 LiTFSI & 63 & 199 & C18 LiTFSI & 63 & 199 \\ C18 MS0.05 & 64 & 188 & C18 ES0.05 & 63 & 184 & C18 IPS0.05 & 62 & 183 \\ C18 MS0.1 & 64 & 170 & C18 ES0.1 & 63 & 172 & C18 IPS0.1 & 62 & 160 \\ C18 MS0.2 & 64 & 153 & C18 ES0.2 & 62 & 149 & C18 IPS0.2 & 61 & 137 \\ C18 MS0.3 & 64 & 139 & C18 ES0.3 & 61 & 121 & C18 IPS0.3 & 59 & 112 \\ C18 MS0.5 & 63 & 117 & C18 ES0.5 & 59 & 88 & C18 IPS0.5 & 56 & 92 \\ C18 MS1.0 & 61 & 93 & C18 ES1.0 & 57 & — & C18 IPS1.0 & 47 & 65 \\ C18 MS & 76/79 & — & C18 ES & 82 & — & C18 IPS & 58/31 & — \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Temperature values of the crystallization points (\(\mathbf{T_{c}}\)) and isotropic to smectic transitions for all pure compounds and mixtures.