Evidence for a thermotropic phase transition in oleic acid

Oleic acid has been investigated by Rayleigh–Brillouin spectroscopy. The temperature gradient of the hypersonic frequency shift and elastic stiffness constant show anomalous behaviour in the range 14–18 °C. This suggests that oleic acid undergoes a change of phase to form a locally nematic structure ca. 5 °C above the melting point. Complementary measurements of viscosity, density and refractive index support this interpretation.