Tilt angle change of nematic liquid crystal as a function of the number of graphite layers

Abstract

The tilt angle of a nematic liquid crystal on a graphite flake was observed to change with increasing numbers of graphite layers. A portion of the substrate that induced homeotropic alignment was covered with graphite flakes, which induced a planar alignment. Nematic liquid crystals placed on the graphite deviated from vertical orientation to the polar angle. The angle of deviation appeared to be proportional to the number of layers and reached a limit, with almost planar alignment, at about 7–8 graphite layers. Although the main contributing factor to the tilt angle change was considered to be the result of van der Waals forces, it was seen that other long-range interaction forces needed to be considered to explain the experimental results obtained.

Keywords:

• nematic liquid crystal
• graphite
• tilt angle
• alignment
• graphene

Acknowledgements

J.-H. Kim is grateful to Dr D.H. Ha for preparation of the samples. The study was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (2010–0023379).