A bent‐core dopant‐induced smectic A* twist state†

†. †This paper is dedicated to Sven T. Lagerwall on the occasion of his 70th birthday

Abstract

The phase behaviour of a commercial calamitic ferroelectric liquid crystal mixture, doped with different mesogenic and non‐mesogenic bent‐core molecules was investigated through polarising microscopy, optical measurements and quenched growth. A twisted smectic structure, similar but not equivalent to a twist grain boundary (TGB) phase, and absent in the neat FLC mixture, was verified. The twisted smectic state can only be observed on cooling and its stability depends on the rate of temperature decrease, which indicates a kinetically governed behaviour. Further, the growth dynamics of the low temperature uniform SmA* bookshelf structure is dominated by viscosity instead of free energy density, as would be expected for a true thermodynamic phase transition. The investigations signify the chiral induction capability of achiral, bent‐core dopant molecules and we believe that the observed behaviour represents the onset of TGB formation at very large pitch. It can thus give valuable information for the fundamental physical understanding of twist grain boundary phase formation.

†. †This paper is dedicated to Sven T. Lagerwall on the occasion of his 70th birthday

Acknowledgements

The authors would like to thank W. Weissflog (Halle) for providing the bent‐core compounds, R. Wingen (Clariant) for supplying the FLC host and K. Tarumi (Merck) for the chiral dopant. We further thank H. Gleeson for very valuable discussions. Financial support from the Nuffield Foundation and the University of Manchester Research Support Fund is gratefully acknowledged. P.A. would like to thank the EPSRC for studentship finance.

Notes

†. †This paper is dedicated to Sven T. Lagerwall on the occasion of his 70th birthday