Spontaneous bend patterns in homochiral ferroelectric SmCP films: evidence for a negative effective bend constant

Abstract

We describe the spontaneous formation of striped and labyrinthine textures of the c-director in freely suspended polar smectic SmCPF films of a bent-core mesogen. Those films develop an instability of the uniform director field. The texture decomposes into local domains of alternating bend. Both right- and left-handed bends of the director occur with equal probability, independently of the overall chirality defined by the local structure of the SmCPF phase. Thus, despite the overall chirality, the system prefers a ground state with bend deformations of both handedness (ambidextrous) of the director. In this paper we suggest a theoretical explanation of this spontaneous bend of the c-director. We assume a negative effective bend elastic constant, in order to explain the formation and optical appearance of the observed stripe and labyrinthine patterns.