Surface Tension Obtained from Various Smectic Free-Standing Films: The Molecular Origin of Surface Tension

High-resolution surface tension measurements have been carried out on the free-standing films of more than 30 selected liquid-crystal compounds in their smectic phases. Surface tension (γ) values falling into major categories of 27, 24, 21, 13, and 11.5 dyn/cm have been obtained. The dependence of γ on specific terminal groups or molecular structures will be discussed. Our results provide important information about the molecular origin of surface tension.