Behavior of the layer compression modulus as a function of frequency near the nematic-smectic-A and re-entrant nematic-smectic-A phase transitions

A progressive cross-over of the layer compression modulus B from a simple power law behavior to a saturation behavior when the frequency is increased from 1 Hz to 2 . 10(3) Hz is observed for the first time near the nematic-smectic-A and the re-entrant nematic-smectic-A phase transitions of a mixture of 4-cyano-4'-(n-hexyloxy)biphenyl and 4-cyano-4'-(n-octyloxy)biphenyl (6OCB-8OCB). This result shows that the saturation of B determined by second sound near the nematic-smectic-A phase transition of a similar mixture is dynamic in nature, and cannot be associated with the static saturation effect predicted by the dislocation loop model, as proposed previously.