Anomalous effects in experiments on monodomain nematic and lamellar phases of the caesium pentadecafluorooctanoate(CsPFO)/water system

Abstract

The effects of defects on a variety of experiments on monodomain nematic and lamellar phases of the CsPFO/water system are described. In NMR experiments the observed anomalous behaviour depends on whether the sample tube is oriented with its long axis perpendicular or parallel to the direction of the applied magnetic field. In the former case, focal domains are shown to lead to a distortion of the spectra on heating, but not on cooling the sample; whereas, in the latter case, dislocations (possibly of the edge variety) are generated on cooling and focal domains on heating. Similar defects can lead to anomalous effects in measurements of bulk properties such as the electrical conductivity, as demonstrated here. In density measurements on unoriented samples using a vibrating capillary densitometer, anomalous decreases in density are observed at the isotropic-to-nematic and nematic-to-lamellar phase transitions. These anomalies are absent in density measurements using a classical dilatometer.