Phase behaviour of an antiferroelectric liquid crystal studied by Raman spectroscopy

Raman scattering investigations were carried out on the liquid crystal, 4-(methylheptyoxycarbonyl)phenyl4'-dodecyloxybiphenyl-4-carboxylate, which exhibits both antiferroelectric and ferroelectric phases. The occurrence, scattering intensity and position of peaks associated with different parts of the molecule are reported as a function of temperature across the solid, liquid crystalline and isotropic phases. The results indicate a significant change in molecular configuration at the solid to liquid crystal and liquid crystal to isotropic phase transitions, the core adopting its most planar configuration in the crystal phase. Finally, an unusual temperature dependence of the position of the Raman peak associated with the phenyl C-C stretching mode is noted within the SmC*(alpha) phase.