Local Frederiks transitions near a solid/nematic interface

Abstract

We consider a solid/nematic interface where long range van der Waals torques favor homeotropic alignment, while a direct steric effect tends to induce a planar alignment. Depending on the relative strength of the two contributions, one may find two transitions : planar ↔ conical and conical ↔ homeotropic. This is reminiscent of recent observations by Ryschenkow and Kléman on glass surfaces coated with carbon black. Similar local Frederiks transitions could occur by competition between two distinct planar arrangments