Facets of smectic A droplets I. Shape measurements

John Bechhoefer , Lubor Lejcek , Patrick Oswald

We have measured profiles of smectic A droplets in air as a function of temperature for several different materials. When small droplets are cooled below the nematic-smectic A transition temperature TAN , they show a single facet whose radius is proportional to (TAN-T)α. The exponent α differs for different materials but is consistent with that measured for the layer compression modulus B. In addition, we measure the shape of curved regions of the surface adjacent to the facet. A power-law fit gives an exponent that varies with both temperature and material and in any case is different from the universal value of 3/2. We also study how droplet shapes relax to equilibrium and find that while the relaxation time for shape changes upon cooling is less than one minute, that for heating ranges from hours to days, depending on TAN. An estimate of the energy barrier to nucleating now layers suggests that process is forbidden and that another explanation of the relaxation-rate asymmetry must be found.

Domaines: Articles anciens

John Bechhoefer, Lubor Lejcek, Patrick Oswald. Facets of smectic A droplets I. Shape measurements. Journal de Physique II, 1992, 2 (1), pp.27-44. ⟨10.1051/jp2:1992111⟩. ⟨jpa-00247610⟩