Control of the orientation of thin open supported columnar liquid crystal films by the kinetics of growth

We report a study of the growth and of the orientation of thin open supported columnar liquid crystal films by thermal annealing. We show that there is a competition between planar and homeotropic orientations ( columns respectively oriented parallel and perpendicular to the solid substrate) of the liquid crystal, which can be controlled by the kinetics of annealing. A model based on the different surface tensions of the system is proposed to account for the experimental observations. Such a control of the alignment opens the way towards discotics based optoelectronic devices.