A correlation between short range smectic-like ordering and the elastic constants of nematic liquid crystals

Abstract

The measurements of the bend (k 33 ) and splay (K 11 ) elastic constants and the amplitude of the smecticlike local ordering (obtained using X-ray diffraction techniques), have been made for a wide range of nematogens. The results reveal a strong correlation between k 33 /k 11 and the strength of the smectic-like local ordering. This correlation applies to nematogens with either bilayer or monolayer structures, irrespective of whether or not they exhibit a smectic phase. These results have been rationalized in more detail in terms of a recent theoretical model which calculated the elastic constants as a function of smectic-like local ordering Mesure des constantes elastiques de corubure (k 33 ) et de deformation en eventail (k 11 ) ainsi que de l'amplitude de l'ordre local de type smectique pour un large ensemble de nematogenes. Mise en evidence d'une forte correlation entre k 33 /k 11 et l'intensite de l'ordre local de type smectique. Cette correlation s'applique a des nematogenes de structure bicouche ou monocouche