study of liquid crystalline N -[4-(4- n -alkoxybenzoyloxy)-2-hydroxybenzylidene]methylanilines

Abstract

New homologous series of N-[4-(4-n-alkoxybenzoyloxy)-2-hydroxybenzylidene]methylanilines[nAHmM (n 5 1-8/10; m 5 2: ortho, m 5 3: meta, m 5 4: para) ] were synthesized. They exhibited a nematic phase except for 1AH3M. The temperature dependence of their Raman spectra was observed in the spectral range of 900-1700 cmÕ 1. In one group of nAHmM compounds, the Raman band at about 1360 cmÕ 1 abruptly decreased in intensity and wavenumber when the crystalline solid-liquid crystal phase transition was approached. In another group, the corresponding band increased through the phase transition. The bands have been assigned to the coupling mode between the in-plane CCH deformational vibration and the ring-N stretching vibration. Such a behaviour can be explained by the molecular conformation with diOE erent twist angles of the aniline ring in relation to the SchiOE's base plane of the molecule. Some nAHmMs exhibited photochromism.