DYNAMICS OF PHASE-TRANSITIONS IN A LIQUID-CRYSTALLINE COMPOUND (TBDA)PROBED BY RAMAN-SPECTROSCOPY

The precise value of linewidths obtained after correcting for the slit width effect for five Raman bands associated with the core of a liquid crystalline compound, terepthal-bis-decyl aniline (TBDA), have been s tudied in the temperature range of 12-472 K. The variation of the line width with temperature confirms two already reported phase transitions at 346 and 427 K. However, the phase transition at 427 K is not purel y first order as reported earlier, but of mixed order in nature. From the measured linewidths of the nu(phi-N) and nu(C=N) modes below room temperature, the estimated activation energy for rotation along the ph i-N bond closely matches with the S-I-S-C phase transition temperature suggesting that the rotation about the phi-N bond is closely linked w ith this transition.