Ellipsometric Study of Free-Standing Films of a Liquid Crystal Possessing Ferroelectric, Ferrielectric, and Antiferroelectric Phases

We present an ellipsometric study of free-standing films of a chiral smectic liquid crystal possessing the phase sequence smectic- A -smectic- C α -smectic- C -smectic- C γ -smectic- C A . The various subphases of the conventional smectic- C phase, which are assumed to have different structures concerning the direction of the molecular tilt in the neighbouring smectic layers, still exist in thin films consisting of only five molecular layers. In the smectic- C α phase, in thick films structural changes occur which are not present in films thinner than ≈ 15 layers. With the exception of the smectic- C γ -smectic- C A transition, all transition temperatures increase with decreasing film thickness.