The structural evolution of films of the liquid crystal mixture mx5112 in the Sm-A and Sm-C* phases has been studied using X-ray scattering techniques. Liquid crystal (LC) films spread on glass substrates with relief grating of 10µm period are subjected to competing boundary conditions on opposite sides. On one side, the LC-air interface imposes a homeotropic boundary condition while on the other the glass substrate with grating generally imposes a homogeneous boundary condition. Near room temperature, the smectic layer normal is oriented parallel to the grating lines on the substrate. The measured srnectic layer spacing reveals oscillations between a Sm-C* and a Sm-A like structures which depend on the film thickness as well as the distance from LC-air interface and is attributable to the difference in the molecular tilt imposed by a. the air-LC interface; b. the substrate; and c. the gratings' internal walls.
X-Ray Scattering Study of a Smectic-A Liquid Crystal Partially Confined Between Free Surface and Microgrooved Substrates01/01/1997
X-ray scattering is used to probe the smectic order in octylcyanobiphenyl partially confined between a free surface and a microgrooved glass substrate. It is found that the smectic order develops 6 K above the bulk nematic to smectic-A transition with layer spacing compressed up to 3% under a lateral confinement within the grooves. This lateral confinement is released as the thickness of the film above the grooves increases.