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 SmCP_F 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 SmCP_F 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.