Atomic force microscopic studies of thin oriented films of ferroelectric liquid crystalline elastomers with varying network architecture

Abstract

Cross-linked ferroelectric liquid crystalline (FLC) polymers were studied by atomic force microscopy (AFM). Polysiloxane copolymers were synthesized with mesogenic and photo-cross-linkable side groups, the latter connected either directly to the backbone via a short spacer or as a terminal group on a part of the mesogens. These elastomers were prepared as thin, freely suspended films in homeotropic orientation. Topographic measurements depict plateaus separated by steps of characteristic height corresponding to the surfaces and edges of smectic layers. From the temperature behavior, as well as from the reaction to mechanical deformation, a model for the network architectures is proposed. In the first case (“intralayer cross-linking”), a predominantly two-dimensional network is formed within the backbone layers separating the smectic layers; in the second case (“interlayer cross-linking”), a three-dimensional network is established that is dependent on the mesophase present during cross-linking.