Raman spectroscopic study of liquid crystalline N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]-chloroanilines

N-[4-(4-n-Alkoxybenzoyloxy)-2-hydroxy-benzylidene]-chloroanilines[nAHmC(n; n=1-8, m; m=2: ortho, m=3: meta. m=4: para)] were synthesized. They exhibit ed a nematic phase. In addition. 8AH4C exhibited the smectic C and A phases , The temperature dependence of their Raman spectra has been observed in th e spectral range of 20-1800 cm(-1). In a group of nAHmC. the Raman band at about 980 cm(-1) decreased in intensity and wavenumber through the solid-li quid crystal phase transition. In the other group, the corresponding band i ncreased through the phase transition. The bands have been assigned to the CH out-of-plane vibration(980 cm(-1)) of the benzene ring. Such a behavior can be explained by the molecular conformations with different twist angles of the aniline ring to the salicylaldimino part of the molecule in conjunc tion with information gained in the photochromic studies of N-2-hydroxy-ben zylidenanilines. The temperature dependence of the 1190 cm(-1) band ascribe d to the ring-N bond stretching vibration gave support to the result of the CH deformation vibration.