Elastic constants of an achiral smectic-C material

A Freedericksz transition technique was used to measure the elastic constants of a smectic-C material with positive dielectric anisotropy. The layer geometry was determined via x-ray scattering and the Freedericksz transition was monitored both optically and from the field-dependent intensity of the Bragg peaks. The splay elastic constant, k 11 , was measured across the nematic phase range and correlated with the B 2 c -director distortion in the smectic-C phase. An estimate of the sum of the layer bending elastic constants was also made and it was found that Ā 21 + Ā 11 is negative and takes a value around 10-4 N. © 2002 Taylor & Francis.