A COMPARATIVE LASER RAMAN-STUDY ON TB4A, TB7A AND TB10A

The basic structural differences between three thermotropic liquid cry stals TB4A, TB7A and TB10A have been interpreted by analysing their Ra man spectra. Three spectral regions, 925-1025, 1275-1475 and 1525-1650 cm(-1), have been chosen in this context to incorporate their structu ral dissimilarity. The induced planarity of the backbone, as an effect of increasing chain length, has been studied by observing the changes in the respective Raman spectra of the three compounds. A tentative a ssignment of all the modes observed in the region 400-1700 cm(-1) is m ade in this context. The molecular conformations of the three compound s have been predicted in their solution states, and are compared with the molecular environment that exists in their liquid crystalline stat es. Structural disorder at the solid-SmG transition is discussed and t he changes are incorporated systematically.