Structure of the cholesteric focal conic domains at the free surface

Atomic force microscope examinations of the free surface and of microtome cuts of a cholesteric oligomer are reported. The obtained images lead to a model of the structure of cholesteric focal conic domains that appear spontaneously at the free surface. These domains develop in order to fulfill the boundary condition at the free surface together with a planar bulk texture. Estimations of the free energy confirm this model. © 1996 The American Physical Society.