Development of new coarse-grained models for chromonic liquid crystals: insights from top-down approaches

ABSTRACT

Two top-down coarse-grained molecular simulation models for a chromonic liquid crystal, 3,6,7,10,11-hexa-(1,4,7-trioxa-octyl)-triphenylene, are tested. We use an extension of the well-known MARTINI model and develop a new coarse-grained model based on statistical associating fluid theory (SAFT)-γ perturbation theory. For both models, we demonstrate self-assembly in the isotropic phase of the chromonic and we test the effectiveness of both models in terms of the structures of the chromonic aggregates that are produced in solution and the thermodynamics of association. The latter is tested by calculations of the potential of mean force for dimers in solution, which measures the strength of molecular association. SAFT-γ provides valuable insights into the thermodynamics of assembly. Exploration of a range of interactions between unlike sites demonstrates that chromonic self-assembly only occurs in a small parameter space where the hydrophilic–lipophilic balance between aromatic core and ethylene oxide chains is optimal. Outside of this balance, chromonic self-assembly is replaced by the formation of conglomerates of molecules or short stacks.

Graphical Abstract

KEYWORDS:

• Chromonic
• simulation
• modelling
• coarse-grained
• thermodynamics

Acknowledgements

The authors would like to acknowledge the support of the Engineering and Physical Sciences Research Council (EPSRC) in the United Kingdom: [Grant Number EP/J004413/1] and Durham University for the use of its HPC facility, Hamilton. TDP would like to thank EPSRC for the award of a studentship. The authors would like to thank PSE Ltd. for the use of its numerical solvers provided by the gSAFT package.

Disclosure statement

No potential conflict of interest was reported by the authors.

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Funding

This work was supported by the Engineering and Physical Sciences Research Council: [Grant Number EP/J004413/1].