Induction of smectic behaviour in a carborane‐containing mesogen. Tail fluorination of a three‐ring nematogen and its miscibility with benzene analogues

Abstract

Partial tail fluorination of a nematic three‐ring carborane mesogen, 1H, induced smectic A (SmA) and smectic C (SmC) phases, leaving a narrow range nematic phase in 1F. In contrast, fluorination of the benzene and bicyclo[2.2.2]octane analogues, 2H and 3H, eliminated their nematic behaviour, enhanced their respective SmC and SmA phases and induced SmA, smectic I (SmI) and smectic F (SmF) phases in 2F. A binary phase diagram of 1F with its non‐fluorinated analogue 1H shows nearly ideal miscibility. In the approximately equimolar mixture of 1F and 2H the SmC phase is expanded by 36 K, and in a mixture of 1F and 2F the SmA phase is stabilised by additional 37 K.

Keywords:

• tail fluorination
• smectic phase induction
• carborane mesogen

Acknowledgements

Partial financial support for this work was received from the National Science Foundation (DMR‐0606317). We are grateful to Prof. R. Dabrowski for the gift of a sample of acid 4F, Prof. Y. Endo for a sample of phenol 5 and Dr. E. Poetsch of E. Merck for the gift of phenol 6.