http://orcid.org/0000-0001-9816-9661
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ABSTRACT
Eight novel liquid crystalline materials were prepared containing highly branched terminal chains, either 2,4,4-trimethylpentyl or 3,5,5-trimethylhexyl. All materials exhibit nematic mesophases, with additional smectic (Sm) C, hexatic B and SmI phases for certain homologues. Analysis by small- and wide-angle X-ray scattering reveals continual build-up of the correlation length within the nematic phases, where we also observe splitting of the small angle peak into four lobes, indicating pretransitional Sm fluctuations. Connoscopy confirms the nematic phase to be uniaxial and optically positive. We observe that in the solid state, the molecules exist as staggered antiparallel pairs as a consequence of the sterically demanding bulky terminal group, and this would also appear to manifest in the hexatic B phase, where the layer spacing was found to be greater than the molecular length. If true, this is an example of pair formation driven by sterics rather than dipole–dipole interactions and suggests that reentrant systems driven purely by steric frustration may be found.
GRAPHICAL ABSTRACT
Acknowledgments
We would like to thank the Engineering and Physical Sciences Research Council (EPSRC) for support of this work via grant codes EP/K039660/1 and EP/M020584/1, and Dr. E. J. Davis for useful discussions. Crystal structures of 10 and 14 have been deposited with the CCDC. Raw data are available upon request from the University of York data catalogue. The authors thank the referee for constructive advice and comments during the peer review process.
Disclosure statement
No potential conflict of interest was reported by the authors.
Supplementary material
Supplementary data can be accessed here.
