Shape Measurements of Faceted Smectic A Droplets

We have measured profiles of smectic A droplets in air as a function of temperature. As the droplet is cooled below the nematic-smectic A transition temperature T NA , the facet radius is proportional to ( T NA − T ) α , with α = 0.45 ± 0.1, an exponent consistent with that measured for the layer compression modulus B . While the relaxation time for shape changes upon cooling is less than one minute, that for heating ranges from hours to days, depending on ( T NA − T ). An estimate of the energy barrier to nucleating new layers suggests that that process is forbidden and that another explanation of the relaxation-rate asymmetry must be found.