Molecular model for the anticlinic smectic-C(A) phase

Both phenomenological and molecular-statistical theories of the anticlinic smectic-C(A) phase (Sm-C(A)) are considered in detail. The anticlinic structure produces antiferroelectricity in the chiral smectic-C(A) phase (Sm-C(A)*). The molecular theory is based on a simple model potential which stabilizes Sm-C(A) with respect to the synclinic smectic-C phase (Sm-C). Conventional dispersion and steric interactions between mesogenic molecules generally do not promote Sm-C(A). It may be stabilized by interlayer orientational correlations between transverse molecular dipoles located in the flexible chains. Such correlations are not sensitive to molecular handedness (chirality), and thus the theory accounts for the formation of the anticlinic phase in racemic mixtures. The model is also confirmed by other experimental data. Finally a simple phase diagram of the perfectly ordered smectic liquid crystal is presented which contains Sm-A, Sm-C, and Sm-C(A).