Surface tensions of smectic liquid crystals

We determine surface tensions sigma of smectic liquid crystals from the cur vature pressure of smectic films. A new technique is introduced for the com parison of surface tensions of different smectic materials. The method is b ased on the relation of curvatures of smectic films drawn on communicating vessels. The measurement of the temperature dependence of sigma reveals ano malies in the vicinity of phase transitions to low temperature smectic modi fications. This anomalous slope d sigma /dT can be related to the surface e xcess entropy of the material in the corresponding temperature range. The s urface tension values determined for a number of mesogens fit well into the classification proposed by Mach et al.