Dynamics of phase transitions in a liquid crystalline compound (TBDA) probed by Raman spectroscopy

The precise value of linewidths obtained after correcting for the slitwidth effect for five Raman bands associated with the core of a liquid crystalline compound, terepthal-bis-decyl aniline (TBDA), have been studied in the temperature range of 12-472 K. The variation of the linewidth with temperature confirms two already reported phase transitions at 346 and 427 K. However, the phase transition at 427 K is not purely first order as reported earlier, but of mixed order in nature. From the measured linewidths of the N and CDN modes below room temperature, the estimated activation energy for rotation along the -N bond closely matches with the SI -SC phase transition temperature suggesting that the rotation about the -N bond is closely linked with this transition.

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