ELLIPSOMETRIC STUDY OF FREESTANDING FILMS OF A LIQUID-CRYSTAL POSSESSING FERROELECTRIC, FERRIELECTRIC, AND ANTIFERROELECTRIC PHASES

We present an ellipsometric study of free-standing films of a chiral s mectic liquid crystal possessing the phase sequence -C(alpha)-smectic- C-smectic-C(gamma)-smectic-C(A). The various subphases of the conventi onal smectic-C phase, which are assumed to have different structures c oncerning the direction of the molecular tilt in the neighbouring smec tic layers, still exist in thin films consisting of only five molecula r layers. In the smectic-C(alpha) phase, in thick films structural cha nges occur which are not present in films thinner than - 15 layers. Wi th the exception of the smectic-C(gamma)-smectic-C(A) transition, all transition temperatures increase with decreasing film thickness.