Emergent chirality in achiral liquid crystals: insights from molecular simulation models of the behaviour of bent-core mesogens

ABSTRACT

We report insights into the behaviour of achiral bent-core liquid crystals using (a) atomistic models of the PnOPIMB series of mesogens and (b) simple coarse-grained models that demonstrate the spontaneous transfer of chirality between molecules by preferential selection of chiral conformations. The models explain the unusual phenomena that chiral interactions can lead to an increase in chirality (decrease in pitch) of a bulk cholesteric liquid crystal when doped with an achiral material. We demonstrate also that chiral interactions are sufficiently strong to induce nanophase separation of an achiral mesogen within a liquid crystal phase, into nanodomains of opposite handedness by preferential selection of conformations that are instantaneously chiral (i.e. nanophase separation of $R$ and $S$ conformations of a molecule that is strictly achiral). We suggest that this unusual behaviour contributes to the templating of chiral structures in bulk phases and, hence, to many of the extraordinary properties of bent-core mesogens that include the formations of helical nanofilaments and the chiral dark conglomerate phase.

Graphical Abstract

KEYWORDS:

• Chiral
• bent-core mesogens
• molecular modelling
• computer simulation

Acknowledgments

MRW and MW would like to thank EPSRC for funding under grants EP/J004413/1 and EP/P007864/1. JSL would like to acknowledge funding from an IdEx (Initiative d’Excellence) Bordeaux Junior Chair. We would like to thank Professor Claudio Zannoni for valuable discussions over many years, and for his insights into the simulation of liquid crystal systems. We gratefully acknowledge conversations with Professors Vanakaras and Photinos in Erice and elsewhere, which have provided many insights into the behaviour of bent-core systems.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was supported by the Engineering and Physical Sciences Research Council [EP/J004413/1,EP/P007864/1].