To investigate the changes in these vibrational modes during the phase transitions, peaks were fit using OriginPro in both the 1000-1100 cm -1 region and 1350-1600 cm -1 region (Figure ). Peak line shape was selected as either Gaussian or Lorentzian based on whether the vibrational mode was associated with the quinoidal core or alkyl chains, respectively. Normally, the line shape in solid crystals is expected to follow a Gaussian curve; however peaks associated with the alkyl chains were fit as Lorentzian due to the disorder, causing more liquid like behavior . In the 1000-1600 cm -1 range, which captures the core and alkyl chain vibrations, we note a significant intensity reduction and redshift of the δ(CH 2 ) peak at 1409 cm - 1 during the I-II transition. We plotted the intensity ratio with respect to ν(C=C) ECC,Q and the peak position to show this sudden drop in intensity and redshift of 7 cm -1 in the δ(CH 2 ) at the I-II transition temperature (Figure ). This trend was repeated across 3 crystals to ensure this change is representative of the I-II transition (Figure ), though the exact transition temperature varied by 5 °C for each crystal due to avalanche behavior. The redshift is indicative of reduced steric hinderance or an increase in the attractive forces between alkyl chains. The intensity decrease, on the other hand, implies alterations to either the orientation or distribution of vibrational states in the alkyl chains. Taken together, these changes show a substantial reorientation of the alkyl chains occurs during the I-II transition. For the II-III polymorph transition, we see large changes in the unit cell, as polymorph III appears to form a likely hexagonal crystal system (Figure ), obtained from the GIXD pattern as discussed in previous work . This is consistent with other previous observations which have shown crystals have a propensity to increase in symmetry at higher temperatures . GIXD video of the II-III transition (Figure , Movie S13) showed the significant reduction in observable peaks, as a result of increased symmetry of the hexagonal lattice as well as reduced long-range order as higher q peaks are no longer measurable (to be discussed later). Despite the reduced diffraction of other Bragg rods at higher q values, the π-stacking peak remains intense and well defined in polymorph III, in line with a continued dominant π-stacking motif. The reconstructive transition is further highlighted by observing the complete disappearance of the polymorph II diffraction peaks at the expense of polymorph III peaks (Figure ), with no shift in position prior to transition, which is consistent with a nucleation and growth type mechanism.