Next, we turn to the evolution of ddG with temperature at fixed composition. An example with xA = 0.3 is shown in Figure ; similar plots for other compositions are shown Figure in the Supplemental Information. As temperature rises, the mixture will initially remain monophasic. However, once the mixture is heated to its phase separation temperature, 30.9 °C for xA= 0.3, the composition of the organic phase will evolve, following the phase equilibrium line (Figure , blue and red points). We might expect that, for a given overall mixture composition, ddG stays approximately constant with increasing temperature in the monophasic region, but decreases in amplitude on going through the phase separation point as the water content in the DIPA-rich phase decreases. Qualitatively, we see such behavior in the ddG signal, as shown in Figures and-D (Supplemental Information). The characteristic ddG signal is evident in the data, and we see the amplitude decreasing from lower (bluer hues) to higher (redder hues) temperatures on warming. Indeed, we see a break in the slope of the signal amplitude with T at the phase transition point of 30.9 °C for xA = 0.3. The xA = 0.9 sample never crosses the phase transition line. Correspondingly, there is no change in the signal amplitude as a function of temperature (Figure ). For amine contents lower than xA = 0.3, macroscopic phase separation caused the x-ray beam to go through the water-rich and not the DIPA-rich phase, as discussed in the SI, and the ddG curves are not meaningful and are not further interpreted.