Surface order reconstruction in nematics

Investigations on pi-cell, a sandwich cell with the director rotating by 180 degrees demonstrate the possibility to obtain nematic transitions between two textures with different topologies, for instance between an untwisted state and a pi-twisted one. These fast textural changes can be obtained by bulk order reconstruction, which allows the director reorientation between two perpendicular directions without macroscopic rotations of the director itself, or by anchoring breaking, which transforms a weak planar anchoring in a homeotropic surface state. Now, we demonstrate that order reconstruction close to a boundary surface with strong or infinite anchoring conditions provides transitions equivalent to anchoring breaking.